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Abstract:

An air conditioner performs a refrigerant quantity judging operation to
judge the refrigerant quantity in a refrigerant circuit, and includes a
heat source unit, utilization units, expansion mechanisms, a first
refrigerant gas pipe, a second refrigerant gas pipe, a refrigerant liquid
pipe, switching mechanisms, bypass circuits, bypass circuit
opening/closing element, and a controller. The switching mechanism can
switch between a first state and a second state. The bypass circuit
opening/closing element are provided in the bypass circuits that bypass
the first refrigerant gas pipe to the second refrigerant gas pipe, and
open and close the bypass circuits. The controller opens the bypass
circuit opening/closing element before performing the refrigerant
quantity judging operation.

Claims:

1. An air conditioner that performs a refrigerant quantity judging
operation to judge the refrigerant quantity in a refrigerant circuit, the
air conditioner comprising:a heat source unit including a heat source
side heat exchanger and a compression element configured to compress
refrigerant gas;a utilization unit including a utilization side heat
exchanger;an expansion mechanism;a first gas refrigerant pipe extending
from a discharge side of the compression element to the utilization
unit;a second gas refrigerant pipe extending from a suction side of the
compression element to the utilization unit;a liquid refrigerant pipe
extending from the heat source side heat exchanger to the utilization
unit;a switching mechanism configured to switch between a first state and
a second state, the refrigerant flowing through the liquid refrigerant
pipe evaporating in the utilization side heat exchanger and thereafter
flowing into the second gas refrigerant pipe in the first state, and the
refrigerant flowing through the first gas refrigerant pipe condensing in
the utilization side heat exchanger and thereafter flowing into the
liquid refrigerant pipe in the second state;a bypass circuit configured
to bypass the first gas refrigerant pipe to the second gas refrigerant
pipe;a bypass circuit opening/closing element provided in the bypass
circuit and configured to open and close the bypass circuit; anda
controller configured to open the bypass circuit opening/closing element
before performing the refrigerant quantity judging operation.

2. The air conditioner according to claim 1, whereinthe bypass circuit
opening/closing element is provided in the heat source unit.

3. The air conditioner according to claim 1, further comprisinga switching
unit separate from the utilization unit and the heat source unit, the
switching unit including the switching mechanism, andthe bypass circuit
opening/closing element being provided in the switching unit.

4. The air conditioner according to claim 1, further comprisinga
temperature detecting element configured to detect the refrigerant
temperature in the first gas refrigerant pipe and output a refrigerant
temperature detection value, andthe controller corrects the refrigerant
quantity judged by the refrigerant quantity judging operation based on
the refrigerant temperature detection value.

5. The air conditioner according to claim 4, whereinthe temperature
detecting element is provided in the switching unit.

6. The air conditioner according to claim 4, whereinthe temperature
detecting element is provided in the heat source unit.

7. The air conditioner according to claim 5, whereinthe temperature
detecting element is provided in the heat source unit.

8. The air conditioner according to claim 2, further comprisinga switching
unit separate from the utilization unit and the heat source unit, the
switching unit including the switching mechanism, andthe bypass circuit
opening/closing element being provided in the switching unit.

9. The air conditioner according to claim 8, further comprisinga
temperature detecting element configured to detect the refrigerant
temperature in the first gas refrigerant pipe and output a refrigerant
temperature detection value, andthe controller corrects the refrigerant
quantity judged by the refrigerant quantity judging operation based on
the refrigerant temperature detection value.

10. The air conditioner according to claim 9, whereinthe temperature
detecting element is provided in the switching unit.

11. The air conditioner according to claim 9, whereinthe temperature
detecting element is provided in the heat source unit.

12. The air conditioner according to claim 2, further comprisinga
temperature detecting element configured to detect the refrigerant
temperature in the first gas refrigerant pipe and output a refrigerant
temperature detection value, andthe controller corrects the refrigerant
quantity judged by the refrigerant quantity judging operation based on
the refrigerant temperature detection value.

13. The air conditioner according to claim 12, whereinthe temperature
detecting element is provided in the switching unit.

14. The air conditioner according to claim 12, whereinthe temperature
detecting element is provided in the heat source unit.

15. The air conditioner according to claim 3, further comprisinga
temperature detecting element configured to detect the refrigerant
temperature in the first gas refrigerant pipe and output a refrigerant
temperature detection value, andthe controller corrects the refrigerant
quantity judged by the refrigerant quantity judging operation based on
the refrigerant temperature detection value.

16. The air conditioner according to claim 15, whereinthe temperature
detecting element is provided in the switching unit.

17. The air conditioner according to claim 15, whereinthe temperature
detecting element is provided in the heat source unit.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a refrigerant circuit of an air
conditioner and an air conditioner provided therewith.

BACKGROUND ART

[0002]Conventionally, an approach has been proposed in which a simulation
of refrigeration cycle characteristics is performed and the excess or
deficiency of the refrigerant quantity is judged by using a result of the
calculation, in order to judge the excess or deficiency of the
refrigerant quantity in a refrigerant circuit of an air conditioner (for
example, see Patent Document 1).

[0003]<Patent Document 1>

[0004]JP-A Publication No. 3-186170

DISCLOSURE OF THE INVENTION

Object to be Achieved by the Invention

[0005]However, according to the technology disclosed in Patent Document 1,
with the multi-air conditioner capable of performing a simultaneous
cooling and heating operation, when performing the refrigerant quantity
judging operation while the cooling operation is performed in all rooms,
the high pressure gas pipe extending from the outdoor unit to the
cooling/heating selection unit will be in a shut-off state on the
cooling/heating selection unit side. Thereby the refrigerant condenses
and accumulates in the pipe and thus the detection error may be
increased.

[0006]An object of the present invention is to control the high pressure
gas pipe so as to reduce the pressure to a low level in order to prevent
accumulation of liquid refrigerant in the high pressure gas pipe
resulting from condensation during the refrigerant quantity judging
operation of the multi-air conditioner capable of performing the
simultaneous cooling and heating operation.

Meant to Achieve the Object

[0007]An air conditioner according to a first aspect of the present
invention is an air conditioner that performs a refrigerant quantity
judging operation to judge the refrigerant quantity in a refrigerant
circuit, the air conditioner including a heat source unit, a utilization
unit, an expansion mechanism, a first gas refrigerant pipe, a second gas
refrigerant pipe, a liquid refrigerant pipe, a switching mechanism, a
bypass circuit, a bypass circuit opening/closing means, and a controller.
The heat source unit includes a compression means that compresses
refrigerant gas and a heat source side heat exchanger. The utilization
unit includes a utilization side heat exchanger. The first gas
refrigerant pipe extends from the discharge side of the compression means
to the utilization unit. The second gas refrigerant pipe extends from the
suction side of the compression means to the utilization unit. The liquid
refrigerant pipe extends from the heat source side heat exchanger to the
utilization unit. The switching mechanism can switch between a first
state and a second state. The first state is a state in which the
refrigerant flowing through the liquid refrigerant pipe evaporates in the
utilization side heat exchanger and then flows into the second gas
refrigerant pipe. The second state is a state in which the refrigerant
flowing through the first gas refrigerant pipe condenses in the
utilization side heat exchanger and then flows into the liquid
refrigerant pipe. The bypass circuit bypasses the first gas refrigerant
pipe to the second gas refrigerant pipe. The bypass circuit
opening/closing means is provided in the bypass circuit and opens and
closes the bypass circuit. The controller opens the bypass circuit
opening/closing means before performing the refrigerant quantity judging
operation.

[0008]In this air conditioner, the refrigerant pipe comprises two gas pipe
systems, and the switching mechanism switches between the first state
(cooling state) and the second state (heating state). Thereby the air
conditioner can be freely set to the cooling operation and the heating
operation. With this air conditioner capable of performing a simultaneous
cooling and heating operation, the refrigerant quantity judging operation
is performed by, for example, setting all the rooms (all the utilization
units) to the first state (cooling state) by the switching mechanism
(cooing/heating selection unit). However, because the first gas
refrigerant pipe (high pressure gas pipe) extending from the heat source
unit to the switching mechanism will be in a shut-off state, the
refrigerant condenses and accumulates in the pipe, which may increase the
detection error.

[0009]Therefore, in this present invention, the bypass circuit
opening/closing means (bypass valve) that bypasses the first gas
refrigerant pipe to the second gas refrigerant pipe is provided, and the
bypass circuit opening/closing means (bypass valve) is set to an opened
state during the refrigerant quantity judging operation, thereby reducing
the pressure difference between the first gas refrigerant pipe and the
second gas refrigerant pipe and preventing accumulation of liquid
refrigerant in the first gas refrigerant pipe resulting from
condensation. Thus, the refrigerant quantity judging operation with high
accuracy can be achieved.

[0010]An air conditioner according to a second aspect of the present
invention is the air conditioner according to the first aspect of the
present invention, wherein the bypass circuit opening/closing means is
provided in the heat source unit.

[0011]In this air conditioner, the bypass circuit opening/closing means is
provided in the heat source unit. Accordingly, the bypass circuit can be
provided in the refrigerant circuit even without laying pipes for the
bypass circuit at the time of construction. Therefore, it is possible to
reduce the labors for construction and the cost.

[0012]An air conditioner according to a third aspect of the present
invention is the air conditioner according to the first or second aspect
of the present invention, further including a switching unit. The
switching unit is a unit different from the heat source unit and the
utilization unit. The switching unit includes the switching mechanism.
The bypass circuit opening/closing means is provided in the switching
unit.

[0013]With this air conditioner, the bypass circuit opening/closing means
is provided in the switching unit. The refrigerant hardly flows through
the first gas refrigerant pipe when the bypass circuit opening/closing
means is provided only in the heat source unit. Therefore, there is a
possibility that the temperate of the gas refrigerant in the pipe may
change because of the incoming heat from the outside air and thereby the
density of the refrigerant may change, which may increase the detection
error.

[0014]Thus, in the present invention, the bypass circuit opening/closing
means that bypasses the first gas refrigerant pipe to the second gas
refrigerant pipe is provided in the switching unit. By using this bypass
circuit opening/closing means together with the bypass circuit
opening/closing means provided in the heat source unit, the low pressure
gas refrigerant is caused to easily flow through the first gas
refrigerant pipe. Therefore, it is possible to prevent the temperature of
the gas refrigerant in the pipe from being changed by the incoming heat
from the outside air and to reduce the detection error. In addition, the
bypass circuit can be provided in the refrigerant circuit even without
laying pipes for the bypass circuit at the time of construction.
Accordingly, it is possible to reduce the labors for construction and the
cost.

[0015]An air conditioner according to a fourth aspect of the present
invention is the air conditioner according to any one of the first
through third aspects of the present invention, further including a
temperature detecting means. The temperature detecting means detects the
refrigerant temperature in the first gas refrigerant pipe and outputs a
refrigerant temperature detection value. The controller corrects the
refrigerant quantity judged by the refrigerant quantity judging operation
based on the refrigerant temperature detection value.

[0016]In this air conditioner, the refrigerant does not easily flow
through the first gas refrigerant pipe even after the first gas
refrigerant pipe is bypassed to the second gas refrigerant pipe by the
provision of the bypass circuit and the distribution of the refrigerant
gas pressure in the pipe is equalized. Therefore, there is a possibility
that the temperate of the gas refrigerant in the pipe may change because
of the incoming heat from the outside air and thereby the density of the
refrigerant may change, which may increase the detection error.

[0017]Thus, in the present invention, the temperature detecting means is
provided in the first gas refrigerant pipe, and the density of the
refrigerant in the pipe is corrected by utilizing the refrigerant
temperature detection value. Thereby it is possible to reduce the
detection error. Thus, the refrigerant quantity judging operation with
higher accuracy can be achieved.

[0018]An air conditioner according to a fifth aspect of the present
invention is the air conditioner according to the fourth aspect of the
present invention, wherein the temperature detecting means is provided in
the switching unit.

[0019]In this air conditioner, the temperature detecting means is mounted
on the first gas refrigerant pipe in the switching unit. Therefore, the
temperature detecting means can be mounted on the first gas refrigerant
pipe even without providing the temperature detecting means to the
refrigerant communication pipe at the time of construction. Therefore, it
is possible to reduce the labors for construction and the cost.

[0020]An air conditioner according to a sixth aspect of the present
invention is the air conditioner according to the fourth or fifth aspect
of the present invention, wherein the temperature detection device is
provided in the heat source unit.

[0021]In this air conditioner, the temperature detecting means is mounted
on the first gas refrigerant pipe in the heat source unit. Therefore, the
temperature detecting means can be mounted on the first gas refrigerant
pipe even without providing the temperature detecting means to the
refrigerant communication pipe at the time of construction. Therefore, it
is possible to reduce the labors for construction and the cost. In
addition, by using this temperature detecting means together with the
temperature detecting means provided in the switching unit in the fifth
aspect of the present invention, it is possible to more accurately
correct the density of the refrigerant in the pipe.

EFFECTS OF THE INVENTION

[0022]In the air conditioner according to the first aspect of the present
invention, the bypass circuit opening/closing means (bypass valve) that
bypasses the first gas refrigerant pipe to the second gas refrigerant
pipe is provided, and the bypass circuit opening/closing means is set to
an opened state during the refrigerant quantity judging operation,
thereby reducing the pressure difference between the first gas
refrigerant pipe and the second gas refrigerant pipe and preventing
accumulation of liquid refrigerant in the first gas refrigerant pipe
resulting from condensation. Thus, the refrigerant quantity judging
operation with high accuracy can be achieved.

[0023]In the air conditioner according to the second aspect of the present
invention, the bypass circuit can be provided in the refrigerant circuit
even without laying pipes for the bypass circuit at the time of
construction. Therefore, it is possible to reduce the labors for
construction and the cost.

[0024]In the air conditioner according to the third aspect of the present
invention, the bypass circuit opening/closing means that bypasses the
first gas refrigerant pipe to the second gas refrigerant pipe is provided
in the switching unit, and the low pressure gas refrigerant is caused to
easily flow through the first gas refrigerant pipe by using this bypass
circuit opening/closing means together with the bypass circuit
opening/closing means provided in the heat source unit. Accordingly, it
is possible to prevent the temperature of the gas refrigerant in the pipe
from being changed by the incoming heat from the outside air and to
reduce the detection error. In addition, the bypass circuit can be
provided in the refrigerant circuit even without laying pipes for the
bypass circuit at the time of construction. Therefore, it is possible to
reduce the labors for construction and the cost.

[0025]With the air conditioner according to the fourth aspect of the
present invention, the temperature detecting means is provided in the
first gas refrigerant pipe, and the density of the refrigerant in the
pipe is corrected by utilizing the refrigerant temperature detection
value. Thereby it is possible to reduce the detection error. Thus, the
refrigerant quantity judging operation with higher accuracy can be
achieved.

[0026]In the air conditioner according to the fifth aspect of the present
invention, the temperature detecting means can be mounted on the first
gas refrigerant pipe even without providing the temperature detecting
means to the refrigerant communication pipe at the time of construction.
Therefore, it is possible to reduce the labors for construction and the
cost.

[0027]In the air conditioner according to the sixth aspect of the present
invention, the temperature detecting means can be mounted on the first
gas refrigerant pipe even without providing the temperature detecting
means to the refrigerant communication pipe at the time of construction.
Therefore, it is possible to reduce the labors for construction and the
cost. In addition, by using this temperature detecting means together
with the temperature detecting means provided in the switching unit in
the fifth aspect of the present invention, it is possible to more
accurately correct the density of the refrigerant in the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a schematic configuration view of an air conditioner
according to an embodiment of the present invention.

[0029]FIG. 2 is a control block diagram of the air conditioner.

[0030]FIG. 3 is a flowchart of a test operation mode.

[0031]FIG. 4 is a flowchart of an automatic refrigerant charging
operation.

[0032]FIG. 5 is a schematic diagram to show a state of the refrigerant
flowing in a refrigerant circuit in a refrigerant quantity judging
operation (illustrations of a four-way switching valve and the like are
omitted).

[0033]FIG. 6 is a flowchart of a pipe volume judging operation.

[0034]FIG. 7 is a Mollier diagram to show a refrigerating cycle of the air
conditioner in the pipe volume judging operation for a liquid refrigerant
communication pipe.

[0035]FIG. 8 is a Mollier diagram to show a refrigerating cycle of the air
conditioner in the pipe volume judging operation for a gas refrigerant
communication pipe.

[0036]FIG. 9 is a flowchart of an initial refrigerant quantity detection
operation.

[0037]FIG. 10 is a flowchart of a refrigerant leak detection operation
mode.

[0052]In the following, an embodiment of an air conditioner according to
the present invention is described based on the drawings.

(1) CONFIGURATION OF THE AIR CONDITIONER

[0053]FIG. 1 is a schematic configuration view of an air conditioner 1
according to an embodiment of the present invention. The air conditioner
1 is a device that is used to cool and heat a room in a building and the
like by performing a vapor compression-type refrigeration cycle
operation. The air conditioner 1 mainly includes one outdoor unit 2 as a
heat source unit, a plurality (three in the present embodiment) of indoor
units 3a to 3c as utilization units connected in parallel to the outdoor
unit 2, connection units 4a to 4c provided respectively correspondingly
to the indoor units 3a to 3c, a first refrigerant communication pipe
group 5 that interconnects the outdoor unit 2 and the connection units 4a
to 4c, and a second refrigerant communication pipe group 7 that
interconnects the connection units 4a to 4c and the indoor units 3a to
3c. The first refrigerant communication pipe group 5 is configured by a
first liquid refrigerant communication pipe 51, a high pressure gas
refrigerant communication pipe 52, and a low pressure gas refrigerant
communication pipe 53, and the second refrigerant communication pipe
group 7 is configured by second liquid refrigerant communication pipes
71a to 71c and second gas refrigerant communication pipes 72a to 72c.
This air conditioner 1 is configured to be able to perform a simultaneous
cooling and heating operation according to the demand of the
air-conditioned space in a room, where the indoor units 3a to 3c are
installed, for example, as in the case where a cooling operation is
performed in one air-conditioned space and a heating operation is
performed in another air conditioned-space or the like. In other words,
the vapor compression-type refrigerant circuit 10 of the air conditioner
1 in the present embodiment is configured by the interconnection of the
outdoor unit 2, the indoor units 3a to 3c, the connection units 4a to 4c,
the first refrigerant communication pipe group 5, and the second
refrigerant communication pipe group 7.

[0054]<Indoor Unit>

[0055]The indoor units 3a to 3c are installed by being embedded in or hung
from a ceiling of a room in a building and the like or by being mounted
or the like on a wall surface of a room. The indoor units 3a to 3c are
connected to the connection units 4a to 4c via the second refrigerant
communication pipe group 7, and configure a part of the refrigerant
circuit 10.

[0056]Next, the configurations of the indoor units 3a to 3c are described.
Note that, because the indoor units 3a, 3b, and 3c all have the same
configuration, only the configuration of the indoor unit 3a is described
here, and in regard to the configurations of the indoor units 3b and 3c,
reference symbols Xb and Xc are used instead of reference symbols Xa
representing the respective portions of the indoor unit 3a, and
descriptions of those respective portions are omitted. For example, an
indoor fan 32a of the indoor unit 3a corresponds to indoor fans 32b and
32c of the indoor units 3b and 3c.

[0057]The indoor unit 3a mainly includes an indoor side refrigerant
circuit 30a that configures a part of the refrigerant circuit 10. The
indoor side refrigerant circuit 30a mainly includes an indoor expansion
valve V9a as an expansion mechanism and an indoor heat exchanger 31a as a
utilization side heat exchanger.

[0058]The indoor expansion valve V9a is an electrically powered expansion
valve connected to the liquid side of the indoor heat exchanger 31a in
order to adjust the flow rate or the like of the refrigerant flowing in
the indoor side refrigerant circuit 30a.

[0059]The indoor heat exchanger 31a is a fin-and-tube type heat exchanger
of a cross fin system configured by a heat transfer tube and numerous
fins, and is a heat exchanger that functions as an evaporator for the
refrigerant during the cooling operation to cool the indoor air and
functions as a condenser for the refrigerant during the heating operation
to heat the indoor air.

[0060]In addition, the indoor unit 3a includes the indoor fan 32a as a
ventilation fan for sucking indoor air into the unit, causing the air to
heat exchange with the refrigerant in the indoor heat exchanger 31a, and
then supplying the air to the room as supply air. The indoor fan 32a is a
fan capable of varying an air flow rate Wr of the air which is supplied
to the indoor heat exchanger 31a, and in the present embodiment, is a
centrifugal fan, multi-blade fan, or the like, which is driven by a motor
33a comprising a DC fan motor.

[0061]In addition, various sensors are disposed in the indoor unit 3a. A
liquid side temperature sensor T9a that detects the temperature of the
refrigerant (i.e., the refrigerant temperature corresponding to a
condensation temperature Tc during the heating operation or an
evaporation temperature Te during the cooling operation) is disposed at
the liquid side of the indoor heat exchanger 31a. A gas side temperature
sensor T10a that detects a temperature Teo of the refrigerant is disposed
at the gas side of the indoor heat exchanger 31a. A room temperature
sensor T11a that detects the temperature of the indoor air that flows
into the unit (i.e., a room temperature Tr) is disposed at the indoor air
suction side of the indoor unit 3a. In the present embodiment, the liquid
side temperature sensor T9a, the gas side temperature sensor T10a, and
the room temperature sensor T11a comprise thermistors. In addition, the
indoor unit 3a includes an indoor side controller 34a that controls the
operation of each portion constituting the indoor unit 3a. Additionally,
the indoor side controller 34a includes a microcomputer, a memory and the
like disposed in order to control the indoor unit 3a, and is configured
such that it can exchange control signals and the like with a remote
controller (not shown) for individually operating the indoor unit 3a,
exchange control signals and the like with the outdoor unit 2 and the
connection units 4a to 4c via a transmission line 8a, and the like.

[0062]<Outdoor Unit>

[0063]The outdoor unit 2 is installed outside of a building and the like,
is connected to the connection units 4a to 4c via the first refrigerant
communication pipe group 5, configuring the refrigerant circuit 10.

[0064]Next, the configuration of the outdoor unit 2 is described. The
outdoor unit 2 mainly includes an outdoor side refrigerant circuit 20
that configures a part of the refrigerant circuit 10. This outdoor side
refrigerant circuit 20 mainly includes a compressor 21, a four-way
switching valve V1, an outdoor heat exchanger 22 as a heat source side
heat exchanger, an outdoor expansion valve V2 as an expansion mechanism,
an accumulator 23, a subcooler 24 as a temperature adjustment mechanism,
a first bypass refrigerant circuit 27, a pressure reducing circuit 28, a
liquid side stop valve V4, and a high pressure gas side stop valve V5, a
low pressure gas side stop valve V6, and a first high pressure gas on/off
valve V8.

[0065]The compressor 21 is a compressor whose operation capacity can be
varied, and in the present embodiment, is a positive displacement-type
compressor driven by a motor 21a whose rotation frequency Rm is
controlled by an inverter. In the present embodiment, only one compressor
21 is provided, but it is not limited thereto, and two or more
compressors may be connected in parallel according to the number of
connected units of indoor units and the like.

[0066]The four-way switching valve V1 is a valve provided for causing the
outdoor heat exchanger 22 to function as an evaporator and a condenser.
The four-way switching valve V1 is connected to the refrigerant gas side
of the outdoor heat exchanger 22, the accumulator 23 on the suction side
of the compressor 21, the discharge side of the compressor 21, and the
pressure reducing circuit 28. Additionally, when causing the outdoor heat
exchanger 22 to function as a condenser, the discharge side of the
compressor 21 is connected to the refrigerant gas side of the outdoor
heat exchanger 22, and the accumulator 23 on the suction side of the
compressor 21 is connected to the pressure reducing circuit 28. On the
other hand, when causing the outdoor heat exchanger 22 to function as an
evaporator, the refrigerant gas side of the outdoor heat exchanger 22 is
connected to the accumulator 23 on the suction side of the compressor 21,
and the discharge side of the compressor 21 is connected to the pressure
reducing circuit 28.

[0067]The outdoor heat exchanger 22 is a heat exchanger capable of
functioning as an evaporator for the refrigerant and also as a condenser
for the refrigerant. In this embodiment, it is a fin-and-tube type heat
exchanger of a cross fin system that exchanges heat with the refrigerant
using air as a heat source. The gas side of the outdoor heat exchanger 22
is connected to the four-way switching valve V1, and the liquid side
thereof is connected to the first liquid refrigerant communication pipe
51.

[0068]The outdoor expansion valve V2 is an electrically powered expansion
valve connected to the liquid side of the outdoor heat exchanger 22 in
order to adjust the pressure, flow rate, or the like of the refrigerant
flowing in the outdoor side refrigerant circuit 20.

[0069]In addition, the outdoor unit 2 includes an outdoor fan 25 as a
ventilation fan for sucking outdoor air into the unit, causing the air to
exchange heat with the refrigerant in the outdoor heat exchanger 22, and
then exhausting the air to the outside. The outdoor fan 25 is a fan
capable of varying an air flow rate Wo of the air which is supplied to
the outdoor heat exchanger 22, and in the present embodiment, is a
propeller fan or the like driven by a motor 25a comprising a DC fan
motor.

[0070]The accumulator 23 is connected between the four-way switching valve
V1 and the compressor 21, and is a container capable of accumulating
excess refrigerant generated in the refrigerant circuit 10 in accordance
with the change in the operation load of the indoor units 3a to 3c and
the like. In addition, the accumulator 23 is connected to the connection
units 4a to 4c via the low pressure gas side stop valve V6 and the low
pressure gas refrigerant communication pipe 53.

[0071]In the present embodiment, the subcooler 24 is a double tube heat
exchanger, and is disposed to cool the refrigerant sent to the indoor
expansion valves V9a to V9c after the refrigerant is condensed in the
outdoor heat exchanger 22. The subcooler 24 is connected between the
outdoor expansion valve V2 and the liquid side stop valve V4.

[0072]In addition, a second bypass refrigerant circuit 6 as a cooling
source of the subcooler 24 is disposed. Note that, in the description
below, a portion corresponding to the refrigerant circuit 10 excluding
the second bypass refrigerant circuit 6 is referred to as a main
refrigerant circuit for convenience sake.

[0073]The second bypass refrigerant circuit 6 is connected to the main
refrigerant circuit so as to cause a portion of the refrigerant sent from
the outdoor heat exchanger 22 to the indoor expansion valves V9a to V9c
via the connection units 4a to 4c to branch from the main refrigerant
circuit and return to the suction side of the compressor 21.
Specifically, the second bypass refrigerant circuit 6 includes a branch
circuit 61 connected so as to branch a portion of the refrigerant sent
from the outdoor expansion valve V2 to the indoor expansion valves V9a to
V9c via the connection units 4a to 4c at a position between the outdoor
heat exchanger 22 and the subcooler 24, and a merging circuit 62
connected to the suction side of the compressor 21 so as to return a
portion of refrigerant from an outlet on the second bypass refrigerant
circuit 6 side of the subcooler 24 to the suction side of the compressor
21. Further, the branch circuit 61 is disposed with a bypass expansion
valve V7 for adjusting the flow rate of the refrigerant flowing in the
second bypass refrigerant circuit 6. Here, the bypass expansion valve V7
comprises an electrically operated expansion valve. In this way, the
refrigerant sent from the outdoor heat exchanger 22 to the indoor
expansion valves V9a to V9c via the connection units 4a to 4c is cooled
in the subcooler 24 by the refrigerant flowing in the second bypass
refrigerant circuit 6 which has been depressurized by the bypass
expansion valve V7. In other words, performance of the subcooler 24 is
controlled by adjusting the opening degree of the bypass expansion valve
V7.

[0074]The first bypass refrigerant circuit 27 is a circuit that bypasses
the pipe between the high pressure gas side stop valve V5 and the
discharge side of the compressor 21 to the pipe between the low pressure
gas side stop valve V6 and the accumulator 23. A first bypass on/off
valve V3 is provided in the first bypass refrigerant circuit 27. Here,
the first bypass on/off valve V3 is a solenoid valve capable of
distributing and blocking the refrigerant.

[0075]The pressure reducing circuit 28 includes a capillary tube C1 and is
connected to the four-way switching valve V1 and the accumulator 23.

[0076]The liquid side stop valve V4, the high pressure gas side stop valve
V5, and the low pressure gas side stop valve V6 are valves disposed at
ports connected to external equipment and pipes (specifically, the first
liquid refrigerant communication pipe 51, the high pressure gas
refrigerant communication pipe 52, and the low pressure gas refrigerant
communication pipe 53). The liquid side stop valve V4 is connected to the
outdoor heat exchanger 22 via the subcooler 24 and the outdoor expansion
valve V2. The high pressure gas side stop valve V5 is connected to the
discharge side of the compressor 21. The low pressure gas side stop valve
V6 is connected to the suction side of the compressor 21 via the
accumulator 23.

[0077]The first high pressure gas on/off valve V8 is provided on the pipe
on the high pressure gas side which is branched from the discharge side
of the compressor 21, and is a solenoid valve capable of distributing and
blocking the high pressure gas refrigerant through the high pressure gas
refrigerant communication pipe 52.

[0078]In addition, various sensors are disposed in the outdoor unit 2.
Specifically, disposed in the outdoor unit 2 are a suction pressure
sensor P1 that detects a suction pressure Ps of the compressor 21, a
discharge pressure sensor P2 that detects a discharge pressure Pd of the
compressor 21, a suction temperature sensor T1 that detects a suction
temperature Ts of the compressor 21, and a discharge temperature sensor
T2 that detects a discharge temperature Td of the compressor 21. The
suction temperature sensor T1 is disposed at a position between the
accumulator 23 and the compressor 21. The outdoor heat exchanger 22 is
provided with a heat exchanger temperature sensor T3 that detects the
temperature of the refrigerant flowing through the outdoor heat exchanger
22 (i.e., the refrigerant temperature corresponding to the condensation
temperature Tc during the cooling operation or the evaporation
temperature Te during the heating operation). A liquid side temperature
sensor T4 that detects a refrigerant temperature Tco is disposed at the
liquid side of the outdoor heat exchanger 22. A liquid pipe temperature
sensor T5 that detects the temperature of the refrigerant (i.e., a liquid
pipe temperature Tlp) is disposed at the outlet on the main refrigerant
circuit side of the subcooler 24. An outdoor temperature sensor T6 that
detects the temperature of the outdoor air that flows into the unit
(i.e., an outdoor temperature Ta) is disposed at the outdoor air suction
side of the outdoor unit 2. The merging circuit 62 of the second bypass
refrigerant circuit 6 is disposed with a bypass temperature sensor T7 for
detecting the refrigerant temperature flowing at the outlet on the second
bypass refrigerant circuit 6 side of the subcooler 24. A first high
pressure gas pipe temperature sensor T8 that detects the temperature of
the refrigerant (i.e., a first high pressure gas pipe temperature Th1) is
provided to the high pressure gas pipe extending from the high pressure
gas side stop valve V5 to the first high pressure gas on/off valve V8. In
the present embodiment, the suction temperature sensor T1, the discharge
temperature sensor T2, the heat exchanger temperature sensor T3, the
liquid side temperature sensor T4, the liquid pipe temperature sensor T5,
the outdoor temperature sensor T6, the bypass temperature sensor T7, and
the first high pressure gas pipe temperature sensor T8 comprise
thermistors.

[0079]In addition, the outdoor unit 2 includes an outdoor side controller
26 that controls the operation of each portion constituting the outdoor
unit 2. Additionally, the outdoor side controller 26 includes a
microcomputer and a memory disposed in order to control the outdoor unit
2, an inverter circuit that controls the motor 21a, and the like, and is
configured such that it can exchange control signals and the like with
the indoor side controllers 34a to 34c of the indoor units 3a to 3c and
connection side controllers 44a to 44c of the connection units 4a to 4c
(described later) via the transmission line 8a. In other words, a
controller 8 that performs the operation control of the entire air
conditioner 1 is configured by the indoor side controllers 34a to 34c,
the connection side controllers 44a to 44c, the outdoor side controller
26, and the transmission line 8a that interconnects each of these
controllers.

[0080]As shown in FIG. 2, the controller 8 is connected so as to be able
to receive detection signals of various sensors P1, P2, T1 to T8, T9a to
T9c, T10a to T10c, T11a to T11c, T12a to T12c and also to be able to
control various equipment and valves 21, 25, 32a to 32c, V1 to V3, V7,
V8, V9a to V9c, V10a to V10c, V11a to V11c, V12a to V12c, V13a to V13c
based on these detection signals and the like. In addition, a warning
display 9 comprising LEDs and the like, which is configured to indicate
that a refrigerant leak is detected in the below described refrigerant
leak detection operation, is connected to the controller 8. Here, FIG. 2
is a control block diagram of the air conditioner 1.

[0081]<Connection Unit>

[0082]The connection units 4a to 4c are installed with the indoor units 3a
to 3c in the room of a building or the like. The connection units 4a to
4c are interposed, together with the first refrigerant communication pipe
group 5 and the second refrigerant communication pipe group 7, between
the indoor units 3a to 3c and the outdoor unit 2, and configure a part of
the refrigerant circuit 10.

[0083]Next, the configurations of the connection units 4a to 4c are
described. Note that, because the connection units 4a, 4b, and 4c all
have the same configuration, only the configuration of the connection
unit 4a is described here, and in regard to the configurations of the
connection units 4b and 4c, reference symbols Yb and Yc are used instead
of reference symbols Ya representing the respective portions of the
connection unit 4a, and descriptions of those respective portions are
omitted. For example, a subcooler 41a of the connection unit 4a
corresponds to subcoolers 41b and 41c of the connection units 4b and 4c.

[0084]The connection unit 4a configures a part of the refrigerant circuit
10 and is provided with a connection side refrigerant circuit 40a. The
connection side refrigerant circuit 40a mainly includes the subcooler
41a, a pressure reducing circuit 42a, a third bypass refrigerant circuit
43a, the low pressure gas on/off valve V10a, and the second high pressure
gas on/off valve V11a.

[0085]The subcooler 41a is a device in which a portion of the liquid
refrigerant to be returned to the first liquid refrigerant communication
pipe 51 is sent to the subcooler 41a via the pressure reducing circuit
42a (described later) so as to subcool the liquid refrigerant to be
returned to the first liquid refrigerant communication pipe 51 when the
indoor units 3a to 3c perform the simultaneous cooling and heating
operation. A portion of the liquid refrigerant introduced into the
subcooler 41a evaporates as a result of heat exchange, and is returned to
the outdoor side refrigerant circuit 20 through the low pressure gas
refrigerant communication pipe 53. The pressure reducing circuit 42a has
a pressure reducing circuit on/off valve V12a and a capillary tube C2a
which are connected in series.

[0086]The third bypass refrigerant circuit 43a is a circuit that bypasses
the high pressure gas refrigerant communication pipe 52 to the low
pressure gas refrigerant communication pipe 53. A second bypass on/off
valve V13a is provided in the third bypass refrigerant circuit 43a. Here,
the second bypass on/off valve V13a is a solenoid valve capable of
distributing and blocking the refrigerant.

[0087]The low pressure gas on/off valve V10a is connected to the low
pressure gas refrigerant communication pipe 53, and is a solenoid valve
capable of distributing and blocking the refrigerant.

[0088]The second high pressure gas on/off valve V11a is connected to the
high pressure gas refrigerant communication pipe 52, and is a solenoid
valve capable of distributing and blocking the refrigerant.

[0089]The connection unit 4a sets the low pressure gas on/off valve V10a
to an opened state and closes the second high pressure gas on/off valve
V11a when the indoor unit 3a performs the cooling operation. Accordingly,
the connection unit 4a can function to send the liquid refrigerant that
flows in from the first liquid refrigerant communication pipe 51 to the
indoor expansion valve V9a of the indoor side refrigerant circuit 30a and
to return the gas refrigerant that is depressurized in the indoor
expansion valve V9a and evaporated in the indoor heat exchanger 31a to
the low pressure gas refrigerant communication pipe 53.

[0090]In addition, the connection unit 4a closes the low pressure gas
on/off valve V10a and sets the second high pressure gas on/off valve V11a
to an opened state when the indoor unit 3a performs the heating
operation. Accordingly, the connection unit 4a can function to send the
high pressure gas refrigerant that flows in from the high pressure gas
refrigerant communication pipe 52 to the gas side of the indoor heat
exchanger 31a in the indoor side refrigerant circuit 30a and to return
the liquid refrigerant condensed in the indoor heat exchanger 31a to the
first liquid refrigerant communication pipe 51.

[0091]In addition, the connection unit 4a is provided with a second high
pressure gas pipe temperature sensor T12a that detects the temperature of
the refrigerant (i.e., a second high pressure gas pipe temperature Th2)
in the high pressure gas refrigerant flow path. In the present
embodiment, the second high pressure gas pipe temperature sensor T12a
comprises a thermistor.

[0092]Further, the connection unit 4a includes a connection side
controller 44a that controls the operation of each portion constituting
the connection unit 4a. Additionally, the connection side controller 44a
includes a microcomputer and a memory disposed in order to control the
indoor unit 4a, and is configured such that it can exchange control
signals and the like with the indoor side controller 34a of the indoor
unit 3a.

[0093]As described above, the outdoor side refrigerant circuit 20 is
connected to the indoor side refrigerant circuits 30a to 30c via the
connection side refrigerant circuits 40a to 40c, and thereby the
refrigerant circuit 10 of the air conditioner 1 is configured.
Additionally, the air conditioner 1 in the present embodiment can
performs the so-called simultaneous cooling and heating operation where,
for example, the indoor unit 3c performs the heating operation while the
indoor units 3a and 3b perform the cooling operation, and the like.

[0095]The first refrigerant communication pipe group 5 and the second
refrigerant communication pipe group 7 are refrigerant pipes that are
arranged on site when installing the air conditioner 1 at an installation
location such as a building and the like. Pipes having various lengths
and pipe diameters are used according to the installation conditions such
as an installation location, combination of an outdoor unit, an indoor
unit, and a connection unit, and the like. Accordingly, for example, when
installing a new air conditioner 1, in order to calculate the charging
quantity of the refrigerant, it is necessary to obtain accurate
information regarding the lengths and pipe diameters and the like of the
first refrigerant communication pipe group 5 and the second refrigerant
communication pipe group 7. However, management of such information and
the calculation itself of the refrigerant quantity are difficult. In
addition, when utilizing an existing pipe to renew an indoor unit, an
outdoor unit, or a connection unit, there is a case where information
regarding the lengths and pipe diameters and the like of the first
refrigerant communication pipe group 5 and the second refrigerant
communication pipe group 7 has been lost.

[0096]As described above, the refrigerant circuit 10 of the air
conditioner 1 is configured by the interconnection of the indoor side
refrigerant circuits 30a to 30c, the outdoor side refrigerant circuit 20,
the connection side refrigerant circuits 40a to 40c, the first
refrigerant communication pipe group 5, and the second refrigerant
communication pipe group 7. In addition, it can also be said that this
refrigerant circuit 10 is configured by the second bypass refrigerant
circuit 6 and the main refrigerant circuit excluding the second bypass
refrigerant circuit 6. Additionally, the controller 8 constituted by the
indoor side controllers 34a to 34c, the connection side controllers 44a
to 44c, and the outdoor side controller 26 allows the air conditioner 1
in the present embodiment to operate the cooling operation, the heating
operation, and the simultaneous cooling and heating operation by
switching thereamong by the four-way switching valve V1 and the first
high pressure on/off valve V8 in the outdoor unit 2 and the low pressure
gas on/off valve V10a and the second high pressure gas on/off valve V11a
in the connection units 4a to 4c, and also to control each equipment of
the outdoor unit 2, the indoor units 3a to 3c, and the connection units
4a to 4c according to the operation load of each of the indoor units 3a
to 3c.

(2) OPERATION OF THE AIR CONDITIONER

[0097]Next, the operation of the air conditioner 1 in the present
embodiment is described.

[0098]The operation modes of the air conditioner 1 in the present
embodiment include: a normal operation mode where control of constituent
equipment of the outdoor unit 2, the indoor units 3a to 3c, and the
connection units 4a to 4c is performed according to the operation load of
each of the indoor units 3a to 3c; a test operation mode where a test
operation to be performed after installation of constituent equipment of
the air conditioner 1 is performed (specifically, it is not limited to
after the first-time installation of equipment: it also includes, for
example, after modification by adding or removing constituent equipment
such as an indoor unit, after repair of damaged equipment, and the like);
and a refrigerant leak detection operation mode where, after the test
operation is finished and the normal operation has started, whether or
not the refrigerant is leaking from the refrigerant circuit 10 is judged.

[0099]The normal operation mode mainly includes the following operations
according to the cooling and heating load of the indoor units 3a to 3c:
the cooling operation where all the indoor units 3a to 3c perform
cooling; the heating operation where all the indoor units 3a to 3c
perform heating; and the simultaneous cooling and heating operation where
one or some of the indoor units 3a to 3c perform cooling and the other
indoor unit(s) performs heating. In addition, according to the
air-conditioning load of the entire indoor units 3a to 3c, the
simultaneous cooling and heating operation can be divided into a case
where the operation is performed by causing the outdoor heat exchanger 22
of the outdoor unit 2 to function as an evaporator (evaporation operation
state), and a case where the operation is performed by causing the
outdoor heat exchanger 22 of the outdoor unit 2 to function as a
condenser (condensation operation state). Note that, the simultaneous
cooling and heating operation described here specifically refers to, for
example, an operation where the indoor unit 3a performs the cooling
operation and the other indoor units 3b and 3c perform the heating
operation.

[0100]In addition, the test operation mode mainly includes an automatic
refrigerant charging operation to charge refrigerant into the refrigerant
circuit 10; a pipe volume judging operation to detect the volumes of the
first refrigerant communication pipe group 5 and the second refrigerant
communication pipe group 7; and an initial refrigerant quantity detection
operation to detect the initial refrigerant quantity after installing
constituent equipment or after charging refrigerant into the refrigerant
circuit 10.

[0101]Operation in each operation mode of the air conditioner 1 is
described below.

[0102]<Normal Operation Mode>

[0103](Cooling Operation)

[0104]First, the cooling operation in the normal operation mode is
described with reference to FIGS. 1 and 2.

[0105]During the cooling operation, in the outdoor side refrigerant
circuit 20 of the outdoor unit 2, the four-way switching valve V1 is
switched to a state indicated by solid lines in FIG. 1, and thereby the
outdoor heat exchanger 22 is caused to function as a condenser. The
outdoor expansion valve V2 is in a fully opened state. The liquid side
stop valve V4, the high pressure gas side stop valve V5, and the low
pressure gas side stop valve V6 are set to an opened state, and the first
high pressure gas on/off valve V8 is set to a closed state.

[0106]In the indoor units 3a to 3c, the opening degree of each of the
indoor expansion valves V9a to V9c is adjusted such that a superheating
degree SHr of the refrigerant at the outlet of each of the indoor heat
exchangers 31a to 31c (i.e., the gas sides of the indoor heat exchangers
31a to 31c) becomes constant at a target superheating degree SHrs. In the
present embodiment, the superheating degree SHr of the refrigerant at the
outlet of each of the indoor heat exchangers 31a to 31c is detected by
subtracting the refrigerant temperature (which corresponds to the
evaporation temperature Te) detected by the liquid side temperature
sensors T9a to T9c from the refrigerant temperature detected by the gas
side temperature sensors T10a to T10c, or is detected by converting the
suction pressure Ps of the compressor 21 detected by the suction pressure
sensor P1 to saturation temperature corresponding to the evaporation
temperature Te, and subtracting this saturation temperature of the
refrigerant from the refrigerant temperature detected by the gas side
temperature sensors T10a to T10c. Note that, although it is not employed
in the present embodiment, a temperature sensor that detects the
temperature of the refrigerant flowing through each of the indoor heat
exchangers 31a to 31c may be disposed such that the superheating degree
SHr of the refrigerant at the outlet of each of the indoor heat
exchangers 31a to 31c is detected by subtracting the refrigerant
temperature corresponding to the evaporation temperature Te which is
detected by this temperature sensor from the refrigerant temperature
detected by the gas side temperature sensors T10a to T10c.

[0107]In addition, the opening degree of the bypass expansion valve V7 is
adjusted such that a superheating degree SHb of the refrigerant at the
outlet on the second bypass refrigerant circuit 6 side of the subcooler
24 becomes a target superheating degree SHbs. In the present embodiment,
the superheating degree SHb of the refrigerant at the outlet on the
second bypass refrigerant circuit 6 side of the subcooler 24 is detected
by converting the suction pressure Ps of the compressor 21 detected by
the suction pressure sensor P1 to saturation temperature corresponding to
the evaporation temperature Te, and subtracting this saturation
temperature of the refrigerant from the refrigerant temperature detected
by the bypass temperature sensor T7. Note that, although it is not
employed in the present embodiment, a temperature sensor may be disposed
at an inlet on the second bypass refrigerant circuit 6 side of the
subcooler 24 such that the superheating degree SHb of the refrigerant at
the outlet on the second bypass refrigerant circuit 6 side of the
subcooler 24 is detected by subtracting the refrigerant temperature
detected by this temperature sensor from the refrigerant temperature
detected by the bypass temperature sensor T7.

[0108]In the connection units 4a to 4c, the second high pressure gas
on/off valves V11a to V11c are closed, and at the same time, the low
pressure gas on/off valves V10a to V10c are opened. Thereby, the indoor
heat exchangers 31a to 31c of the indoor units 3a to 3c function as
evaporators, and at the same time, a state is achieved where the indoor
heat exchangers 31a to 31c of the indoor units 3a to 3c are connected to
the suction side of the compressor 21 of the outdoor unit 2 via the low
presser gas refrigerant communication pipe 53. In addition, the pressure
reducing circuit on/off valves V12a to V12c are in a closed state.

[0109]When the compressor 21, the outdoor fan 25, and the indoor fans 32a
to 32c are started in this state of the refrigerant circuit 10, the low
pressure gas refrigerant is sucked into the compressor 21 and compressed
into high pressure gas refrigerant. Subsequently, the high pressure gas
refrigerant is sent to the outdoor heat exchanger 22 via the four-way
switching valve V1, exchanges heat with the outdoor air supplied by the
outdoor fan 25, and becomes condensed into high pressure liquid
refrigerant. Then, this high pressure liquid refrigerant passes through
the outdoor expansion valve V2, flows into the subcooler 24, exchanges
heat with the refrigerant flowing in the second bypass refrigerant
circuit 6, is further cooled, and becomes subcooled. At this time, a
portion of the high pressure liquid refrigerant condensed in the outdoor
heat exchanger 22 is branched into the second bypass refrigerant circuit
6 and is depressurized by the bypass expansion valve V7. Subsequently, it
is returned to the suction side of the compressor 21. Here, the
refrigerant that passes through the bypass expansion valve V7 is
depressurized close to the suction pressure Ps of the compressor 21 and
thereby a portion of the refrigerant evaporates. Then, the refrigerant
flowing from the outlet of the bypass expansion valve V7 of the second
bypass refrigerant circuit 6 toward the suction side of the compressor 21
passes through the subcooler 24 and exchanges heat with high pressure
liquid refrigerant sent from the outdoor heat exchanger 22 on the main
refrigerant circuit side to the indoor units 3a to 3c.

[0110]Then, the high pressure liquid refrigerant in a subcooled state is
sent to the indoor units 3a to 3c via the liquid side stop valve V4, the
first liquid refrigerant communication pipe 51, and each connection units
4a to 4c. The high pressure liquid refrigerant sent to the indoor units
3a to 3c is depressurized close to the suction pressure Ps of the
compressor 21 by the indoor expansion valves V9a to V9c, becomes
refrigerant in a low pressure gas-liquid two-phase state, is sent to the
indoor heat exchangers 31a to 31c, exchanges heat with the indoor air in
the indoor heat exchangers 31a to 31c, and is evaporated into low
pressure gas refrigerant.

[0111]Then, the low pressure gas refrigerant is sent to the low pressure
gas refrigerant communication pipe 53 through the low pressure gas on/off
valves V10a to V10c of the connection units 4a to 4c. This low pressure
gas refrigerant is sent to the outdoor unit 2 via the low pressure gas
refrigerant communication pipe 53, and flows into the accumulator 23 via
the low pressure gas side stop valve V6. Then, the low pressure gas
refrigerant that flowed into the accumulator 23 is again sucked into the
compressor 21.

[0112](Heating Operation)

[0113]During the heating operation, in the outdoor side refrigerant
circuit 20 of the outdoor unit 2, the four-way switching valve V1 is
switched to a state indicated by dotted lines in FIG. 1, and thereby the
outdoor heat exchanger 22 functions as an evaporator. At the same time,
the high pressure gas refrigerant compressed in and discharged from the
compressor 21 is supplied to the indoor units 3a to 3c through the high
pressure gas refrigerant communication pipe 52. The opening degree of the
outdoor expansion valve V2 is adjusted so as to be able to depressurize
the refrigerant that flows into the outdoor heat exchanger 22 to a
pressure where the refrigerant can be evaporated (i.e., an evaporation
pressure Pe) in the outdoor heat exchanger 22. The liquid side stop valve
V4, the high pressure gas side stop valve V5, and the low pressure gas
side stop valve V6 are in an opened state, and the bypass expansion valve
V7 and the first high pressure gas on/off valve V8 are in an opened
state.

[0114]In the indoor units 3a to 3c, the opening degree of each of the
indoor expansion valves V9a to V9c is adjusted such that a subcooling
degree SCr of the refrigerant at the outlet of each of the indoor heat
exchangers 31a to 31c (i.e., the liquid sides of the indoor heat
exchangers 31a to 31c) becomes constant at a target subcooling degree
SCrs. In the present embodiment, the subcooling degree SCr of the
refrigerant at the outlet of each of the indoor heat exchangers 31a to
31c is detected by converting the discharge pressure Pd of the compressor
21 detected by the discharge pressure sensor P2 to saturation temperature
corresponding to the condensation temperature Tc, and by subtracting the
refrigerant temperature detected by the liquid side temperature sensors
T9a to T9c from the refrigerant saturation temperature. Note that,
although it is not employed in the present embodiment, a temperature
sensor that detects the temperature of the refrigerant flowing through
each of the indoor heat exchangers 31a to 31c may be disposed such that
the subcooling degree SCr of the refrigerant at the outlet of each of the
indoor heat exchangers 31a to 31c is detected by subtracting the
refrigerant temperature corresponding to the condensation temperature Tc
which is detected by this temperature sensor from the refrigerant
temperature detected by the liquid side temperature sensors T9a to T9c.

[0115]In the connection units 4a to 4c, as the low pressure gas on/off
valve V10a to V10c are closed and the second high pressure gas on/off
valves V11a to V11c are opened at the same time, the indoor heat
exchangers 31a to 31c of the indoor units 3a to 3c are brought into a
state where they function as condensers. In addition, the pressure
reducing circuit on/off valves V12a to V12c are in an opened state.

[0116]When the compressor 21, the outdoor fan 25, and the indoor fans 32a
to 32c are started in this state of the refrigerant circuit 10, the low
pressure gas refrigerant is sucked into the compressor 21 and compressed
into high pressure gas refrigerant. Then, this high pressure gas
refrigerant is sent to the high pressure gas refrigerant communication
pipe 52 via the four-way switching valve V1 and the high pressure gas
side stop valve V5.

[0117]Then, the high pressure gas refrigerant sent to the high pressure
gas refrigerant communication pipe 52 is sent to each of the connection
units 4a to 4c. The high pressure gas refrigerant sent to the connection
units 4a to 4c is sent to the indoor units 3a to 3a through the second
high pressure gas on/off valves V11a to V11c. The high pressure gas
refrigerant sent to the indoor units 3a to 3c exchanges heat with the
indoor air in the indoor heat exchangers 31a to 31c and is condensed into
high pressure liquid refrigerant. Subsequently, it is depressurized
according to the opening degree of the indoor expansion valves V9a to V9c
when passing through the indoor expansion valves V9a to V9c.

[0118]Then, the refrigerant that passed through the indoor expansion
valves V9a to V9c is sent to the subcoolers 41a to 41c of the connection
units 4a to 4c. This subcooled liquid refrigerant is sent to the outdoor
unit 2 via the first liquid refrigerant communication pipe 51, is further
depressurized via the liquid side stop valve V4 and the outdoor expansion
valve V2, and then flows into the outdoor heat exchanger 22. Then, the
refrigerant in a low pressure gas-liquid two-phase state that flowed into
the outdoor heat exchanger 22 exchanges heat with the outdoor air
supplied by the outdoor fan 25, is evaporated into low pressure gas
refrigerant, and flows into the accumulator 23 via the four-way switching
valve V1. Then, the low pressure gas refrigerant that flowed into the
accumulator 23 is again sucked into the compressor 21.

[0119](Simultaneous Cooling and Heating Operation/Evaporation Load)

[0120]An operation (evaporation operation) is described which is the
simultaneous cooling and heating operation where, for example, among the
indoor units 3a to 3c, the indoor unit 3a performs the cooling operation
and at the same time the indoor units 3b and 3c perform the heating
operation, and in which the outdoor heat exchanger 22 of the outdoor unit
2 is caused to function as an evaporator according to the air
conditioning load of the entire indoor units 3a to 3c. At this time, as
is the case with the above described heating operation mode, the four-way
switching valve V1 is switched to a state indicated by dotted lines in
FIG. 1. Thereby the outdoor heat exchanger 22 functions as an evaporator
and also the high pressure gas refrigerant compressed in and discharged
from the compressor 21 is supplied to the two indoor units 3b and 3c
performing the heating operation through the high pressure gas
refrigerant communication pipe 52. At this time, the bypass expansion
valve V7 is closed, and the first high pressure gas on/off valve V8 is
set to an opened state.

[0121]In the indoor unit 3a, the opening degree of the indoor expansion
valve V9a is adjusted according to the cooling load of the indoor unit
3a. For example, adjustment of the opening degree is performed based on
the superheating degree of the indoor heat exchanger 31a (specifically,
the temperature difference between the refrigerant temperature detected
by the liquid side temperature sensor T9a and the refrigerant temperature
detected by the gas side temperature sensor T10a).

[0122]In the connection unit 4a, the second high pressure gas on/off valve
V 11a is closed and at the same time the low pressure gas on/off valve
V10a is opened. Accordingly, the indoor heat exchanger 31a of the indoor
unit 3a is caused to function as an evaporator and at the same time a
state is achieved where the indoor heat exchanger 31a of the indoor unit
3a is connected to the suction side of the compressor 21 of the outdoor
unit 2 via the low pressure gas refrigerant communication pipe 53. In
addition, the pressure reducing circuit on/off valve V12a is in a closed
state.

[0123]In addition, in the indoor units 3b and 3c, the opening degree of
each of the indoor expansion valves V9b and V9c is adjusted such that the
subcooling degree SCr of the refrigerant at the outlet of each of the
indoor heat exchangers 31b and 31c (i.e., the liquid sides of the indoor
heat exchangers 31b and 31c) becomes constant at the target subcooling
degree SCrs.

[0124]In the connection units 4b and 4c, the low pressure gas on/off
valves V10b and V10c are closed and at the same time the second high
pressure gas on/off valves V11b and V11c are opened. Thereby the indoor
heat exchangers 31b and 31c of the indoor units 3b and 3c are brought
into a state where they function as condensers. In addition, the pressure
reducing circuit on/off valves V12b and V12c are in an opened state.

[0125]In this state of the refrigerant circuit 10, the high pressure gas
refrigerant compressed in and discharged from the compressor 21 is sent
to the high pressure gas refrigerant communication pipe 52 through the
high pressure gas side stop valve V5.

[0126]Then, the high pressure gas refrigerant sent to the high pressure
gas refrigerant communication pipe 52 is sent to each of the indoor units
3b and 3c through each of the connection units 4b and 4c and the second
high pressure gas on/off valves V11b and V11c. Then, the high pressure
gas refrigerant sent to the indoor units 3b and 3c exchanges heat with
the indoor air in the indoor heat exchangers 31b and 31c and is condensed
into high pressure liquid refrigerant. Subsequently, it is depressurized
according to the opening degree of the indoor expansion valves V9b and
V9c when passing through the indoor expansion valves V9b and V9c. On the
other hand, the indoor air is heated and supplied to the room.

[0127]The refrigerant that passed through the indoor expansion valves V9b
and V9c is sent to the subcoolers 41b and 41c of the connection units 4b
and 4c and is subcooled. This subcooled liquid refrigerant is sent to the
first liquid refrigerant communication pipe 51, and a portion of the
liquid refrigerant sent to the first liquid refrigerant communication
pipe 51 is sent to the connection unit 4a. Then, the refrigerant sent to
the connection unit 4a is sent to the indoor expansion valve V9a of the
indoor unit 3a.

[0128]The refrigerant sent to the indoor expansion valve V9a is
depressurized by the indoor expansion valve V9a. Thereafter, the
refrigerant exchanges heat with the indoor air in the indoor heat
exchangers 31a and is thereby evaporated into low pressure gas
refrigerant. On the other hand, the indoor air is cooled and supplied to
the room. Then, the low pressure gas refrigerant is sent to the
connection unit 4a.

[0129]The low pressure gas refrigerant sent to the connection unit 4a is
sent to the outdoor unit 2 through the low pressure gas on/off valve V10a
and the low pressure gas refrigerant communication pipe 53, and flows
into the accumulator 23 via the low pressure gas side stop valve V6.
Then, the low pressure gas refrigerant that flowed into the accumulator
23 is again sucked into the compressor 21.

[0130]On the other hand, the remaining portion of the refrigerant from
which the refrigerant sent from the first liquid refrigerant
communication pipe 51 to the connection unit 4a and the indoor unit 3a is
excluded is sent to the outdoor heat exchanger 22 via the liquid side
stop valve V4 of the outdoor unit 2, is evaporated in the outdoor heat
exchanger 22, and becomes low pressure gas refrigerant. This gas
refrigerant is sucked into the compressor 21 via the four-way switching
valve V1 and the accumulator 23.

[0131](Simultaneous Cooling and Heating Operation/Condensation Load)

[0132]An operation (condensation operation) is described which is the
simultaneous cooling and heating operation mode where, for example, among
the indoor units 3a to 3c, the indoor unit 3a and 3b perform the cooling
operation and at the same time the indoor unit 3c performs the heating
operation, and in which the outdoor heat exchanger 22 of the outdoor unit
2 is caused to function as a condenser according to the air conditioning
load of the entire indoor units 3a to 3c. At this time, the four-way
switching valve V1 is switched to a state indicated by solid lines in
FIG. 1. Thereby the outdoor heat exchanger 22 functions as a condenser
and also the high pressure gas refrigerant compressed in and discharged
from the compressor 21 is supplied to the indoor unit 3c through the high
pressure gas refrigerant communication pipe 52. At this time, the first
high pressure gas on/off valve V8 is set to an opened state.

[0133]In the indoor units 3a and 3b, the opening degree of each of the
indoor expansion valves V9a and V9b is adjusted according to the cooling
load of each of the indoor units 3a and 3b. For example, adjustment of
the opening degree is performed based on the superheating degree of each
of the indoor heat exchangers 31a and 31b (specifically, the temperature
difference between the refrigerant temperature detected by the liquid
side temperature sensors T9a and T9b and the refrigerant temperature
detected by the gas side temperature sensors T10a and T10b,
respectively).

[0134]In the connection units 4a and 4b, the second high pressure gas
on/off valves V11a and V11b are closed and at the same time the low
pressure gas on/off valves V10a and V10b are opened. Thereby, the indoor
heat exchangers 31a and 31b of the indoor units 3a and 3b will function
as evaporators and at the same time a state is achieved where the indoor
heat exchangers 31a and 31b of the indoor units 3a and 3b are connected
to the suction side of the compressor 21 of the outdoor unit 2 via the
low pressure gas refrigerant communication pipe 53. In addition, the
pressure reducing circuit on/off valves V12a and V12b are in a closed
state.

[0135]In the indoor unit 3c, the opening degree of the indoor expansion
valve V9c is adjusted according to the heating load of the indoor unit
3c. For example, adjustment of the opening degree is performed based on
the subcooling degree of the indoor heat exchanger 31c (specifically, the
temperature difference between the refrigerant temperature detected by
the liquid side temperature sensor T9c and the refrigerant temperature
detected by the gas side temperature sensor T10c).

[0136]In the connection unit 4c, the low pressure gas on/off valve V10c is
closed and at the same time the second high pressure gas on/off valve
V11c is opened. Accordingly, a state is achieved where the indoor heat
exchanger 31c of the indoor unit 3c functions as a condenser. In
addition, the pressure reducing circuit on/off valve V12c is in an opened
state.

[0137]In such a state of the refrigerant circuit 10, the high pressure gas
refrigerant compressed in and discharged from the compressor 21 is sent
to the outdoor heat exchanger 22 through the four-way switching valve V1
and is also sent to the high pressure gas refrigerant communication pipe
52 through the high pressure gas side stop valve V5.

[0138]The high pressure gas refrigerant sent to the outdoor heat exchanger
22 is condensed in the outdoor heat exchanger 22 and becomes liquid
refrigerant. Then, the liquid refrigerant is sent to the first liquid
refrigerant communication pipe 51 through the liquid side stop valve V4.

[0139]In addition, the high pressure gas refrigerant sent to the high
pressure gas refrigerant communication pipe 52 is sent to the connection
unit 4c. The high pressure gas refrigerant sent to the connection unit 4c
is sent to the indoor heat exchanger 31c of the indoor unit 3c through
the second high pressure gas on/off valve V11c.

[0140]The high pressure gas refrigerant sent to the indoor heat exchanger
31c exchanges heat with the indoor air in the indoor heat exchanger 31c
of the indoor unit 3c and thereby is condensed. On the other hand, the
indoor air is heated and supplied to the room. The refrigerant condensed
in the indoor heat exchanger 31c passes through the indoor expansion
valve V9c and then is sent to the connection unit 4c.

[0141]The refrigerant sent to the connection unit 4c is sent to the first
liquid refrigerant communication pipe 51, and mergers with the
refrigerant that is sent to the first liquid refrigerant communication
pipe 51 through the liquid side stop valve V4. The refrigerant that flows
through the first liquid refrigerant communication pipe 51 is sent to the
indoor expansion valves V9a and V9b of the indoor units 3a and 3b via the
connection units 4a and 4b.

[0142]The refrigerant sent to the indoor expansion valves V9a and V9b is
depressurized by the indoor expansion valves V9a and V9b. Then, the
refrigerant evaporates as a result of heat exchange with the indoor air
in the indoor heat exchangers 31a and 31b and becomes low pressure gas
refrigerant. On the other hand, the indoor air is cooled and supplied to
the room. Then, the low pressure gas refrigerant is sent to the
connection units 4a and 4b.

[0143]The low pressure gas refrigerant sent to the connection units 4a and
4b is sent to the low pressure gas refrigerant communication pipe 53
through the low pressure gas on/off valves V10a and V10b. The low
pressure gas refrigerant sent to the low pressure gas refrigerant
communication pipe 53 is sucked into the compressor 21 via the low
pressure gas side stop valve V6 and the accumulator 23.

[0144]Such operation control as described above in the normal operation
mode is performed by the controller 8 (more specifically, the indoor side
controllers 34a to 34c, the connection side controllers 44a to 44c, the
outdoor side controller 26, and the transmission line 8a that
interconnects each of the controllers 34a to 34c, 44a to 44c, and 26)
that functions as a normal operation controlling means to perform the
normal operation that includes the cooling operation and the heating
operation.

[0145]<Test Operation Mode>

[0146]Next, the test operation mode is described with reference to FIGS. 1
to 3. Here, FIG. 3 is a flowchart of the test operation mode. In the
present embodiment, in the test operation mode, first, the automatic
refrigerant charging operation in Step S1 is performed. Subsequently, the
pipe volume judging operation in Step S2 is performed, and then the
initial refrigerant quantity detection operation in Step S3 is performed.

[0147]In the present embodiment, an example of a case is described where
the outdoor unit 2 into which the refrigerant is charged in advance, the
indoor units 3a to 3c, and the connection units 4a to 4c are installed at
an installation location such as a building and the like and
interconnected via the first refrigerant communication pipe group 5 and
the second refrigerant communication pipe group 7 to configure the
refrigerant circuit 10; and subsequently additional refrigerant is
charged into the refrigerant circuit 10 whose refrigerant quantity is
insufficient according to the volumes of the first refrigerant
communication pipe group 5 and the second refrigerant communication pipe
group 7.

[0148](Step S1: Automatic Refrigerant Charging Operation)

[0149]First, the liquid side stop valve V4, the high pressure gas side
stop valve V5, and the low pressure gas side stop valve V6 of the outdoor
unit 2 are opened and the refrigerant circuit 10 is filled with the
refrigerant that is charged in the outdoor unit 2 in advance.

[0150]Next, when a worker performing the test operation connects a
refrigerant cylinder for additional charging to a service port (not
shown) of the refrigerant circuit 10 and issues a command to start the
test operation directly to the controller 8 or remotely by a remote
controller (not shown) and the like, the controller 8 starts the process
from Step S11 to Step S13 shown in FIG. 4. Here, FIG. 4 is a flowchart of
the automatic refrigerant charging operation.

[0151](Step S11: Refrigerant Quantity Judging Operation)

[0152]When a command to start the automatic refrigerant charging operation
is issued, with the four-way switching valve V1 of the outdoor unit 2 in
a state indicated by solid lines in FIG. 1, the refrigerant circuit 10
becomes a state where the indoor expansion valves V9a to V9c of the
indoor units 3a to 3c, the low pressure gas on/off valves V10a to V10c of
the connection units 4a to 4c, and the outdoor expansion valve V2 are
opened, and the first high pressure gas on/off valve V8 of the outdoor
unit 2 and the second high pressure gas on/off valves V11a to V11c of the
connection units 4a to 4c are closed. Then, the compressor 21, the
outdoor fan 25, and the indoor fans 32a to 32c are started, and all of
the indoor units 3a to 3c are forcibly caused to perform the cooling
operation (hereinafter referred to as "all indoor unit operation"). At
this time, the first bypass on/off valve V3 in the first bypass
refrigerant circuit 27 in the outdoor unit 2 and the second bypass on/off
valves V13a to V13c in the third bypass refrigerant circuits 43a to 43c
in the connection units 4a to 4c are in an opened state, and the pressure
of the refrigerant in the high pressure gas refrigerant communication
pipe 52 and in the low pressure gas refrigerant communication pipe 53
becomes equalized.

[0153]Consequently, as shown in FIG. 5, in the refrigerant circuit 10, the
high pressure gas refrigerant compressed and discharged in the compressor
21 flows along a flow path from the compressor 21 to the outdoor heat
exchanger 22 that functions as a condenser (see the portion from the
compressor 21 to the outdoor heat exchanger 22 in the area indicated by
diagonal hatching in FIG. 5); the high pressure refrigerant that
undergoes phase-change from a gas state to a liquid state by heat
exchange with the outdoor air flows in the outdoor heat exchanger 22 that
functions as a condenser (see the portion corresponding to the outdoor
heat exchanger 22 in the area indicated by diagonal hatching and black
hatching in FIG. 5); the high pressure liquid refrigerant flows along a
flow path from the outdoor heat exchanger 22 to the indoor expansion
valves V9a to V9c (including the outdoor expansion valve V2, the portion
corresponding to the main refrigerant circuit side of the subcooler 24,
and the first liquid refrigerant communication pipe 51) and a flow path
from the outdoor heat exchanger 22 to the bypass expansion valve V7 (see
the portions from the outdoor heat exchanger 22 to the indoor expansion
valves V9a to V9c and to the bypass expansion valve V7 in the area
indicated by black hatching in FIG. 5); the low pressure refrigerant that
undergoes a phase change from a gas-liquid two-phase state to a gas state
by heat exchange with the indoor air and the like flows in the portions
corresponding to the indoor heat exchangers 31a to 31c that function as
evaporators and the portion corresponding to the second bypass
refrigerant circuit 6 side of the subcooler 24 (see the portions
corresponding to the indoor heat exchangers 31a to 31c and the portion
corresponding to the subcooler 24 in the area indicated by lattice
hatching and diagonal hatching in FIG. 5); and, within a flow path from
the indoor heat exchangers 31a to 31c to the compressor 21, the low
pressure gas refrigerant flows along flow paths on the high pressure gas
side and the low pressure gas side of the connection units 4a to 4c
(including the third bypass refrigerant circuits 43a to 43c), a flow path
including the high pressure gas refrigerant communication pipe 52, the
low pressure gas refrigerant communication pipe 53, the first bypass
refrigerant circuit 27, and the accumulator 23, and a flow path from the
portion corresponding to the second bypass refrigerant circuit 6 side of
the subcooler 24 to the compressor 21 (see the portion from the indoor
heat exchangers 31a to 31c to the compressor 21 ((including the high
pressure gas refrigerant connection pipe 52 and the low pressure gas
refrigerant communication pipe 53 and the connection units 4a to 4c)) and
the portion from the portion corresponding to the second bypass
refrigerant circuit 6 side of the subcooler 24 to the compressor 21 in
the area indicated by diagonal hatching in FIG. 5). FIG. 5 is a schematic
diagram to show a state of the refrigerant flowing in the refrigerant
circuit 10 in a refrigerant quantity judging operation (illustrations of
the four-way switching valve V1 and the like are omitted).

[0154]Next, equipment control as described below is performed to proceed
to operation to stabilize the state of the refrigerant circulating in the
refrigerant circuit 10. Specifically, the indoor expansion valves V9a to
V9c are controlled such that the superheating degree SHr of each of the
indoor heat exchangers 31a to 31c that function as evaporators becomes
constant (hereinafter referred to as "superheating degree control"); the
operation capacity of the compressor 21 is controlled such that the
evaporation pressure Pe becomes constant (hereinafter referred to as
"evaporation pressure control"); the air flow rate Wo of outdoor air
supplied to the outdoor heat exchanger 22 by the outdoor fan 25 is
controlled such that a condensation pressure Pc of the refrigerant in the
outdoor heat exchanger 22 becomes constant (hereinafter referred to as
"condensation pressure control"); the operation capacity of the subcooler
24 is controlled such that the temperature of the refrigerant sent from
the subcooler 24 to the indoor expansion valves V9a to V9c becomes
constant (hereinafter referred to as "liquid pipe temperature control");
and the air flow rate Wr of indoor air supplied to the indoor heat
exchangers 31a to 31c by the indoor fans 32a to 32c is maintained
constant such that the evaporation pressure Pe of the refrigerant is
stably controlled by the above described evaporation pressure control.

[0155]Here, the reason to perform the evaporation pressure control is
because the evaporation pressure Pe of the refrigerant in the indoor heat
exchangers 31a to 31c that function as evaporators is greatly affected by
the refrigerant quantity in the indoor heat exchangers 31a to 31c where
the low pressure refrigerant flows while undergoing a phase change from a
gas-liquid two-phase state to a gas state as a result of heat exchange
with the indoor air (see the portions corresponding to the indoor heat
exchangers 31a to 31c in the area indicated by lattice hatching and
diagonal hatching in FIG. 5, which is hereinafter referred to as
"evaporator portion C"). Then, here, the state of the refrigerant flowing
in the evaporator portion C is stabilized by causing the evaporation
pressure Pe of the refrigerant in the indoor heat exchangers 31a to 31c
to become constant as a result of controlling the operation capacity of
the compressor 21 by the motor 21a whose rotation frequency Rm is
controlled by an inverter. In other words, a state is created in which
the refrigerant quantity in the evaporator portion C changes mainly by
the evaporation pressure Pe. Note that, the control of the evaporation
pressure Pe by the compressor 21 in the present embodiment is achieved in
the following manner: the refrigerant temperature (which corresponds to
the evaporation temperature Te) detected by the liquid side temperature
sensors T9a to T9c of the indoor heat exchangers 31a to 31c is converted
to saturation pressure; the operation capacity of the compressor 21 is
controlled such that the saturation pressure becomes constant at a target
low pressure Pes (in other words, the control to change the rotation
frequency Rm of the motor 21a is performed); and then a refrigerant
circulation flow rate Wc flowing in the refrigerant circuit 10 is
increased or decreased. Note that, although it is not employed in the
present embodiment, the operation capacity of the compressor 21 may be
controlled such that the suction pressure Ps of the compressor 21
detected by the suction pressure sensor P1, which is the operation state
quantity equivalent to the pressure of the refrigerant at the evaporation
pressure Pe of the refrigerant in the indoor heat exchangers 31a to 31c,
becomes constant at the target low pressure Pes, or the saturation
temperature (which corresponds to the evaporation temperature Te)
corresponding to the suction pressure Ps becomes constant at a target low
pressure Tes. Also, the operation capacity of the compressor 21 may be
controlled such that the refrigerant temperature (which corresponds to
the evaporation temperature Te) detected by the liquid side temperature
sensors T9a to T9c of the indoor heat exchangers 31a to 31c becomes
constant at the target low pressure Tes.

[0156]Then, by performing such evaporation pressure control, the state of
the refrigerant flowing through the refrigerant pipes from the indoor
heat exchangers 31a to 31c to the compressor 21 including the low
pressure gas refrigerant communication pipe 53 and the accumulator 23
(see the portion from the indoor heat exchangers 31a to 31c to the
compressor 21 in the area indicated by diagonal hatching in FIG. 5, which
is hereinafter referred to as "gas refrigerant distribution portion D")
becomes stabilized, creating a state where the refrigerant quantity in
the gas refrigerant distribution portion D changes mainly by the
evaporation pressure Pe (i.e., the suction pressure Ps), which is the
operation state quantity equivalent to the pressure of the refrigerant in
the gas refrigerant distribution portion D.

[0157]In addition, the reason to perform the condensation pressure control
is because the condensation pressure Pc of the refrigerant is greatly
affected by the refrigerant quantity in the outdoor heat exchanger 22
where the high pressure refrigerant flows while undergoing a phase change
from a gas state to a liquid state as a result of heat exchange with the
outdoor air (see the portion corresponding to the outdoor heat exchanger
22 in the area indicated by diagonal hatching and black hatching in FIG.
5, which is hereinafter referred to as "condenser portion A"). The
condensation pressure Pc of the refrigerant in the condenser portion A
greatly changes due to the effect of the outdoor temperature Ta.
Therefore, the air flow rate Wo of the indoor air supplied from the
outdoor fan 25 to the outdoor heat exchanger 22 is controlled by the
motor 25a, and thereby the condensation pressure Pc of the refrigerant in
the outdoor heat exchanger 22 is maintained constant and the state of the
refrigerant flowing in the condenser portion A is stabilized. In other
words, a state is created where the refrigerant quantity in the condenser
portion A changes mainly by a subcooling degree SCo at the liquid side of
the outdoor heat exchanger 22 (hereinafter referred to as the outlet of
the outdoor heat exchanger 22 in the description regarding the
refrigerant quantity judging operation). Note that, for the control of
the condensation pressure Pc by the outdoor fan 25 in the present
embodiment, the discharge pressure Pd of the compressor 21 detected by
the discharge pressure sensor P2, which is the operation state quantity
equivalent to the condensation pressure Pc of the refrigerant in the
outdoor heat exchanger 22, or the temperature of the refrigerant flowing
through the outdoor heat exchanger 22 (i.e., the condensation temperature
Tc) detected by the heat exchanger temperature sensor T3 is used.

[0158]Then, by performing such condensation pressure control, the high
pressure liquid refrigerant flows along the flow path from the outdoor
heat exchanger 22 to the indoor expansion valves V9a to V9c (including
the outdoor expansion valve V2, the portion on the main refrigerant
circuit side of the subcooler 24, and the first liquid refrigerant
communication pipe 51) and the flow path from the outdoor heat exchanger
22 to the bypass expansion valve V7 of the second bypass refrigerant
circuit 6, the pressure of the refrigerant in the portions from the
outdoor heat exchanger 22 to the indoor expansion valves V9a to V9c and
to the bypass expansion valve V7 (see the area indicated by black
hatching in FIG. 5, which is hereinafter referred to as "liquid
refrigerant distribution portion B") becomes stabilized, and the liquid
refrigerant distribution portion B is sealed by the liquid refrigerant,
thereby becoming a stable state.

[0159]In addition, the reason to perform the liquid pipe temperature
control is to prevent a change in the density of the refrigerant in the
refrigerant pipes from the subcooler 24 to the indoor expansion valves
V9a to V9c including the first liquid refrigerant communication pipe 51
(see the portion from the subcooler 24 to the indoor expansion valves V9a
to V9c in the liquid refrigerant distribution portion B shown in FIG. 5).
Performance of the subcooler 24 is controlled by increasing or decreasing
the flow rate of the refrigerant flowing in the second bypass refrigerant
circuit 6 such that the refrigerant temperature Tlp detected by the
liquid pipe temperature sensor T5 disposed at the outlet on the main
refrigerant circuit side of the subcooler 24 becomes constant at a target
liquid pipe temperature Tlps, and by adjusting the quantity of heat
exchange between the refrigerant flowing in the main refrigerant circuit
side and the refrigerant flowing in the second bypass refrigerant circuit
6 side of the subcooler 24. Note that, the flow rate of the refrigerant
in the second bypass refrigerant circuit 6 is increased or decreased by
adjustment of the opening degree of the bypass expansion valve V7. In
this way, the liquid pipe temperature control is achieved in which the
refrigerant temperature in the refrigerant pipes from the subcooler 24 to
the indoor expansion valves V9a to V9c including the first liquid
refrigerant communication pipe 51 becomes constant.

[0160]Then, even when the refrigerant temperature Tco at the outlet of the
outdoor heat exchanger 22 (i.e., the subcooling degree SCo of the
refrigerant at the outlet of the outdoor heat exchanger 22) changes along
with an increase in the refrigerant quantity by charging refrigerant into
the refrigerant circuit 10, the effect of a change in the refrigerant
temperature Tco at the outlet of the outdoor heat exchanger 22 will
remain only within the refrigerant pipes from the outlet of the outdoor
heat exchanger 22 to the subcooler 24 as a result of performing such
liquid pipe temperature constant control. Accordingly, the effect of a
change in the refrigerant temperature Tco at the outlet of the outdoor
heat exchanger 22 will not extend to the refrigerant pipes from the
subcooler 24 to the indoor expansion valves V9a to V9c including the
first liquid refrigerant communication pipe 51 in the liquid refrigerant
distribution portion B.

[0161]Further, the reason to perform the superheating degree control is
because the refrigerant quantity in the evaporator portion C greatly
affects the quality of wet vapor of the refrigerant at the outlets of the
indoor heat exchangers 31a to 31c. The superheating degree SHr of the
refrigerant at the outlet of each of the indoor heat exchangers 31a to
31c is controlled such that the superheating degree SHr of the
refrigerant at the gas sides of the indoor heat exchangers 31a to 31c
(hereinafter referred to as the outlets of the indoor heat exchangers 31a
to 31c in the description regarding the refrigerant quantity judging
operation) becomes constant at the target superheating degree SHrs (in
other words, such that the gas refrigerant at the outlet of each of the
indoor heat exchangers 31a to 31c is in a superheat state) by controlling
the opening degree of the indoor expansion valves V9a to V9c, and thereby
the state of the refrigerant flowing in the evaporator portion C is
stabilized.

[0162]Consequently, by performing such superheating degree control, a
state is created in which the gas refrigerant reliably flows in the gas
refrigerant distribution portion D.

[0163]By various control described above, the state of the refrigerant
circulating in the refrigerant circuit 10 becomes stabilized, and the
distribution of the refrigerant quantity in the refrigerant circuit 10
becomes constant. Therefore, when refrigerant starts to be charged into
the refrigerant circuit 10 by additional refrigerant charging, which is
subsequently performed, it is possible to create a state where a change
in the refrigerant quantity in the refrigerant circuit 10 mainly appears
as a change of the refrigerant quantity in the outdoor heat exchanger 22
(hereinafter this operation is referred to as "refrigerant quantity
judging operation").

[0164]Such control as described above is performed as the process in Step
S11 by the controller 8 (more specifically, by the indoor side
controllers 34a to 34c, the connection side controllers 44a to 44c, the
outdoor side controller 26, and the transmission line 8a that
interconnects each of the controllers 34a to 34c, 44a to 44c, 26) that
functions as a refrigerant quantity judging operation controlling means
for performing the refrigerant quantity judging operation.

[0165]Note that, unlike the present embodiment, when refrigerant is not
charged in advance in the outdoor unit 2, it is necessary prior to Step
S11 to charge refrigerant until the refrigerant quantity reaches a level
where constituent equipment will not abnormally stop during the above
described refrigerant quantity judging operation.

[0166](Step S12: Refrigerant Quantity Calculation)

[0167]Next, additional refrigerant is charged into the refrigerant circuit
10 while performing the above described refrigerant quantity judging
operation. At this time, the controller 8 that functions as a refrigerant
quantity calculating means calculates the refrigerant quantity in the
refrigerant circuit 10 from the operation state quantity of constituent
equipment or refrigerant flowing in the refrigerant circuit 10 during
additional refrigerant charging in Step S12.

[0168]First, the refrigerant quantity calculating means in the present
embodiment is described. The refrigerant quantity calculating means
divides the refrigerant circuit 10 into a plurality of portions,
calculates the refrigerant quantity for each divided portion, and thereby
calculates the refrigerant quantity in the refrigerant circuit 10. More
specifically, a relational expression between the refrigerant quantity in
each portion and the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 is set for each divided
portion, and the refrigerant quantity in each portion can be calculated
by using these relational expressions. In the present embodiment, when
the four-way switching valve V1 is in a state indicated by solid lines in
FIG. 1, i.e., a state where the discharge side of the compressor 21 is
connected to the gas side of the outdoor heat exchanger 22 and where the
suction side of the compressor 21 is connected to the outlets of the
indoor heat exchangers 31a to 31c via the low pressure gas side stop
valve V6 and the low pressure gas refrigerant communication pipe 53, the
refrigerant circuit 10 is divided into the following portions and a
relational expression is set for each portion: a portion corresponding to
the compressor 21 and a portion from the compressor 21 to the outdoor
heat exchanger 22 including the four-way switching valve V1 (not shown in
FIG. 5) (hereinafter referred to as "high pressure gas pipe portion E");
a portion corresponding to the outdoor heat exchanger 22 (i.e., the
condenser portion A); a portion from the outdoor heat exchanger 22 to the
subcooler 24 and an inlet side half of a portion corresponding to the
main refrigerant circuit side of the subcooler 24 in the liquid
refrigerant distribution portion B (hereinafter referred to as "high
temperature side liquid pipe portion B1"); an outlet side half of a
portion corresponding to the main refrigerant circuit side of the
subcooler 24 and a portion from the subcooler 24 to the liquid side stop
valve V4 (not shown in FIG. 5) in the liquid refrigerant distribution
portion B (hereinafter referred to as "low temperature side liquid pipe
portion B2"); a portion combining the first liquid refrigerant
communication pipe 51, the liquid side refrigerant flow path of the
connection units 4a to 4c, and the second liquid refrigerant
communication pipe 71a to 71c in the liquid refrigerant distribution
portion B (hereinafter referred to as "liquid refrigerant communication
pipe portion B3"); a portion from the first liquid refrigerant
communication pipe 51 in the liquid refrigerant distribution portion B up
to the second gas refrigerant communication pipes 72a to 72c in the gas
refrigerant distribution portion D including portions corresponding to
the indoor expansion valves V9a to V9c and the indoor heat exchangers 31a
to 31c (i.e., the evaporator portion C) (hereinafter referred to as
"indoor unit portion F"); a portion combining the high pressure gas
refrigerant communication pipe 52 and the high pressure gas side
refrigerant flow path (including up to the second bypass on/off valves
V13a to V13c on the high pressure gas side of the third bypass
refrigerant circuits 43a to 43c) in the connection units 4a to 4c
(hereinafter referred to as "high pressure gas refrigerant communication
pipe portion G1") in the gas refrigerant distribution portion D; a
portion combining the low pressure gas refrigerant communication pipe 53,
the second gas refrigerant communication pipes 72a to 72c, and the low
pressure gas side refrigerant flow path in the connection units 4a to 4c
(including up to the second bypass on/off valves V13a to V13c on the low
pressure gas side of the third bypass refrigerant circuits 43a to 43c)
(hereinafter referred to as "low pressure gas refrigerant communication
pipe portion G2") in the gas refrigerant distribution portion D; a
portion from the high pressure gas side stop valve V5 (not shown in FIG.
5) to the first high pressure gas on/off valve V8 (hereinafter referred
to as "first low pressure low pressure gas pipe portion H") in the gas
refrigerant distribution portion D; a portion combining a portion from
the low pressure gas side stop valve V6 (not shown in FIG. 5) to the
first bypass refrigerant circuit 27 and the first bypass refrigerant
circuit 27 and a portion from the first bypass refrigerant circuit 27 to
the four-way switching valve V1 and a portion from the first bypass
refrigerant circuit 27 to the compressor 21 including the accumulator 23
(hereinafter referred to as "second low pressure gas pipe portion I");
and a portion from the high temperature side liquid pipe portion B1 to
the second low pressure gas pipe portion I including the bypass expansion
valve V7 and a portion corresponding to the second bypass refrigerant
circuit 6 side of the subcooler 24 in the liquid refrigerant distribution
portion B (hereinafter referred to as "second bypass circuit portion J").
Note that the portion combining the high pressure gas refrigerant
communication pipe portion G1 and the low pressure gas refrigerant
communication pipe portion G2 is referred to as a gas refrigerant
communication pipe portion G. Next, the relational expressions set for
each portion described above are described.

[0169]In the present embodiment, a relational expression between a
refrigerant quantity Mog1 in the high pressure gas pipe portion E and the
operation state quantity of constituent equipment or refrigerant flowing
in the refrigerant circuit 10 is expressed, for example, by

Mog1=Vog1×ρd,

which is a function expression in which a volume Vog1 of the high pressure
gas pipe portion E in the outdoor unit 2 is multiplied by a density
ρd of the refrigerant in high pressure gas pipe portion E. Note that,
the volume Vog1 of the high pressure gas pipe portion E is a value that
is known prior to installation of the outdoor unit 2 at the installation
location and is stored in advance in the memory of the controller 8. In
addition, the density ρd of the refrigerant in the high pressure gas
pipe portion E is obtained by converting the discharge temperature Td and
the discharge pressure Pd.

[0170]A relational expression between a refrigerant quantity Mc in the
condenser portion A and the operation state quantity of constituent
equipment or refrigerant flowing in the refrigerant circuit 10 is
expressed, for example, by

Mc=kc1×Ta+kc2×Tc+kc3×SHm+kc4×Wc+kc5×ρc+k-
c6×ρco+kc7,

which is a function expression of the outdoor temperature Ta, the
condensation temperature Tc, a compressor discharge superheating degree
SHm, the refrigerant circulation flow rate Wc, the saturated liquid
density ρc of the refrigerant in the outdoor heat exchanger 22, and a
density ρco of the refrigerant at the outlet of the outdoor heat
exchanger 22. Note that, the parameters kc1 to kc7 in the above described
relational expression are derived from a regression analysis of results
of tests and detailed simulations and are stored in advance in the memory
of the controller 8. In addition, the compressor discharge superheating
degree SHm is a superheating degree of the refrigerant at the discharge
side of the compressor, and is obtained by converting the discharge
pressure Pd to refrigerant saturation temperature and subtracting this
refrigerant saturation temperature from the discharge temperature Td. The
refrigerant circulation flow rate Wc is expressed as a function of the
evaporation temperature Te and the condensation temperature Tc (i.e.,
Wc=f(Te, Tc)). A saturated liquid density ρc of the refrigerant is
obtained by converting the condensation temperature Tc. The density
ρco of the refrigerant at the outlet of the outdoor heat exchanger 22
is obtained by converting the condensation pressure Pc, which is obtained
by converting the condensation temperature Tc, and the refrigerant
temperature Tco.

[0171]A relational expression between a refrigerant quantity Mol1 in the
high temperature side liquid pipe portion B1 and the operation state
quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10 is expressed, for example, by

Mol1=Vol1×ρco,

which is a function expression in which a volume Vol1 of the high
temperature side liquid pipe portion B1 in the outdoor unit 2 is
multiplied by the density ρco of the refrigerant in the high
temperature side liquid pipe portion B1 (i.e., the above described
density of the refrigerant at the outlet of the outdoor heat exchanger
22). Note that, the volume Vol1 of the high pressure side liquid pipe
portion B1 is a value that is known prior to installation of the outdoor
unit 2 at the installation location and is stored in advance in the
memory of the controller 8.

[0172]A relational expression between a refrigerant quantity Mol2 in the
low temperature side liquid pipe portion B2 and the operation state
quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10 is expressed, for example, by

Mol2=Vol2×ρlp,

which is a function expression in which a volume Vol2 of the low
temperature side liquid pipe portion B2 in the outdoor unit 2 is
multiplied by a density pip of the refrigerant in the low temperature
side liquid pipe portion B2. Note that, the volume Vol2 of the low
temperature side liquid pipe portion B2 is a value that is known prior to
installation of the outdoor unit 2 at the installation location and is
stored in advance in the memory of the controller 8. In addition, the
density ρlp of the refrigerant in the low temperature side liquid
pipe portion B2 is the density of the refrigerant at the outlet of the
subcooler 24, and is obtained by converting the condensation pressure Pc
and the refrigerant temperature Tlp at the outlet of the subcooler 24.

[0173]A relational expression between a refrigerant quantity Mlp in the
liquid refrigerant communication pipe portion B3 and the operation state
quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10 is expressed, for example, by

Mlp=Vlp×ρlp,

which is a function expression in which a volume Vlp of the portion
combining the first liquid refrigerant communication pipe 51, the liquid
side refrigerant flow path in the connection units 4a to 4c, and the
second liquid refrigerant communication pipes 71a to 71c is multiplied by
the density pip of the refrigerant in the liquid refrigerant
communication pipe portion B3 (i.e., the density of the refrigerant at
the outlet of the subcooler 24). Here, the volume Vlp is divided into a
volume Vlp1 of the portion combining the first liquid refrigerant
communication pipe 51 and the second liquid refrigerant communication
pipes 71a to 71c and a volume Vlp2 of the liquid side refrigerant flow
path in the connection units 4a to 4c. As for the volume Vlp1 of the
portion combining the first liquid refrigerant communication pipe 51 and
the second liquid refrigerant communication pipes 71a to 71c, because the
first liquid refrigerant communication pipe 51 and the second liquid
refrigerant communication pipes 71a to 71c are refrigerant pipes arranged
on site when installing the air conditioner 1 at an installation location
such as a building and the like, a value calculated on site from the
information regarding the length, pipe diameter and the like is input, or
information regarding the length, pipe diameter and the like is input on
site, and the controller 8 calculates the volume Vlp1 from the input
information of the first liquid refrigerant communication pipe 51 and the
second liquid refrigerant communication pipes 71a to 71c. Or, as
described below, the volume Vlp1 is calculated by using the operation
results of the pipe volume judging operation. In addition, the volume
Vlp2 of the liquid side refrigerant flow path in the connection units 4a
to 4c is a value that is known prior to installation of the connection
units 4a to 4c at the installation location and is stored in advance in
the memory of the controller 8.

[0174]A relational expression between a refrigerant quantity Mr in the
indoor unit portion F and the operation state quantity of constituent
equipment or refrigerant flowing in the refrigerant circuit 10 is
expressed, for example, by

Mr=kr1×Tlp+kr2×ΔT+kr3×SHr+kr4×Wr+kr5,

which is a function expression of the refrigerant temperature Tlp at the
outlet of the subcooler 24, a temperature difference ΔT in which
the evaporation temperature Te is subtracted from the room temperature
Tr, the superheating degree SHr of the refrigerant at the outlets of the
indoor heat exchangers 31a to 31c, and the air flow rate Wr of the indoor
fans 32a to 32c. Note that, the parameters kr1 to kr5 in the above
described relational expression are derived from a regression analysis of
results of tests and detailed simulations and are stored in advance in
the memory of the controller 8. Note that, here, the relational
expression for the refrigerant quantity Mr is set for each of the three
indoor units 3a to 3c, and the entire refrigerant quantity in the indoor
unit portion F is calculated by adding the refrigerant quantity Mr in the
indoor unit 3a, the refrigerant quantity Mr in the indoor unit 3b, and
the refrigerant quantity Mr in the indoor unit 3c. Note that, relational
expressions having parameters kr1 to kr5 with different values will be
used when the model and/or capacity is different among the indoor unit
3a, the indoor unit 3b, and the indoor unit 3c.

[0175]The gas refrigerant communication pipe portion G is divided into a
high pressure gas refrigerant communication pipe portion G1 and a low
pressure gas refrigerant communication pipe portion G2, and a refrigerant
quantity Mgp in the gas refrigerant communication pipe portion G is a
value obtained by adding a refrigerant quantity Mgph in the high pressure
gas refrigerant communication pipe portion G1 and a refrigerant quantity
Mgp1 in the low pressure gas refrigerant communication pipe portion G2.
In addition, a volume Vgp of the gas refrigerant communication pipe
portion G is a value obtained by adding a volume Vgph of the high
pressure gas refrigerant communication pipe portion G1 and a volume Vgp1
of the low pressure gas refrigerant communication pipe portion G2. In
other words, theses relational expressions are expressed as follows.

Mgp=Mgph+Mgp1

Vgp=Vgph+Vgp1

[0176]A relational expression between the refrigerant quantity Mgph in the
high pressure gas refrigerant communication pipe portion G1 and the
operation state quantity of constituent equipment or refrigerant flowing
in the refrigerant circuit 10 is expressed, for example, by

Mgph=Vgph×ρgph,

which is a function expression in which the volume Vgph of the portion
combining the high pressure gas refrigerant communication pipe 52 and the
high pressure gas side refrigerant flow path (including up to the second
bypass on/off valves V13a to V13c on the high pressure gas side of the
third bypass refrigerant circuits 43a to 43c) is multiplied by a density
ρgph of the refrigerant in the high pressure gas refrigerant
communication pipe portion G1. Here, the volume Vgph is divided into a
volume Vgph1 of the high pressure gas refrigerant communication pipe 52
and a volume Vgph2 of the high pressure gas side refrigerant flow path in
the connection units 4a to 4c (including up to the second bypass on/off
valves V13a to V13c on the high pressure gas side in the third bypass
refrigerant circuits 43a to 43c). As for the volume Vgp1 of the high
pressure gas refrigerant communication pipe 52, as is the case with the
portion combining the first liquid refrigerant communication pipe 51 and
the second liquid refrigerant communication pipes 71a to 71c, because the
high pressure gas refrigerant communication pipe 52 is a refrigerant pipe
arranged on site when installing the air conditioner 1 at an installation
location such as a building and the like, a value calculated on site from
the information regarding the length, pipe diameter and the like is
input, or information regarding the length, pipe diameter and the like is
input on site, and the controller 8 calculates the volume Vgp1 from the
input information of the high pressure gas refrigerant communication pipe
52. Or, as described below, the volume Vgp1 is calculated by using the
operation results of the pipe volume judging operation. In addition, the
density ρgph of the refrigerant in the high pressure gas refrigerant
communication pipe portion G1 is an average value among: a density ρs
of the refrigerant at the suction side of the compressor 21, a density
ρoh of the refrigerant in the pipe on the high pressure gas side
between the high pressure gas side stop valve V5 and the first high
pressure gas on/off valve V8 in the outdoor unit 2, a density ρbsh of
the refrigerant in the high pressure gas side refrigerant flow path in
the connection units 4a to 4c, and a density ρeo of the refrigerant
at the outlets of the indoor heat exchangers 31a to 31c (i.e., the inlets
of the second gas refrigerant communication pipes 72a to 72c). The
density ρs of the refrigerant is obtained by converting the suction
pressure Ps and the suction temperature Ts. The density ρoh of the
refrigerant is obtained by converting the first high pressure gas pipe
temperature Th1. The density ρbsh of the refrigerant is obtained by
converting the second high pressure gas pipe temperature Th2. The density
ρeo of the refrigerant is obtained by converting the evaporation
pressure Pe, which is a converted value of the evaporation temperature
Te, and an outlet temperature Teo of each of the indoor heat exchangers
31a to 31c. In addition, the volume Vgp2 of the high pressure gas side
refrigerant flow path in the connection units 4a to 4c (including up to
the second bypass on/off valves V13a to V13c on the high pressure gas
side in the third bypass refrigerant circuits 43a to 43c) is a value that
is known prior to installation of the connection units 4a to 4c at the
installing location and is stored in advance in the memory of the
controller 8.

[0177]A relational expression between the refrigerant quantity Mgp1 in the
low pressure gas refrigerant communication pipe portion G2 and the
operation state quantity of constituent equipment or refrigerant flowing
in the refrigerant circuit 10 is expressed, for example, by

Mgp1=Vgp1×ρgp1,

which is a function expression in which the volume Vgp1 of a portion
combining the low pressure gas refrigerant communication pipe 53, the
second gas refrigerant communication pipes 72a to 72c, and the low
pressure gas refrigerant flow path in the connection units 4a to 4c
(including up to the second bypass on/off valves V13a to V13c on the low
pressure gas side of the third bypass refrigerant circuit 43a to 43c) is
multiplied by a density ρgp1 of the refrigerant in the low pressure
gas refrigerant communication pipe portion G2. Here, the volume Vgp1 is
divided into a volume Vgpl1 of a portion combining the low pressure gas
refrigerant communication pipe 53 and the second gas refrigerant
communication pipes 72a to 72c, and a volume Vgpl2 of the low pressure
gas side refrigerant flow path in the connection units 4a to 4c
(including up to the second bypass on/off valves V13a to V13c on the low
pressure gas side in the third bypass refrigerant circuits 43a to 43c).
As for the volume Vgpl1 of the portion combining the low pressure gas
refrigerant communication pipe 53 and the second gas refrigerant
communication pipes 72a to 72c, as is the case with the portion combining
the first liquid refrigerant communication pipe 51 and the second liquid
refrigerant communication pipes 71a to 71c and also as is the case with
the high pressure gas refrigerant communication pipe 52, because the low
pressure gas refrigerant communication pipe 53 and the second gas
refrigerant communication pipes 72a to 72c are refrigerant pipes arranged
on site when installing the air conditioner 1 at an installation location
such as a building and the like, a value calculated on site from the
information regarding the length, pipe diameter and the like is input, or
information regarding the length, pipe diameter and the like is input on
site, and the controller 8 calculates the volume Vgpl1 from the input
information of the low pressure gas refrigerant communication pipe 53 and
the second gas refrigerant communication pipes 72a to 72c. Or, as
described below, the volume Vgpl1 is calculated by using the operation
results of the pipe volume judging operation. In addition, the density
ρgp1 of the refrigerant in the low pressure gas refrigerant
communication pipe portion G2 is an average value between the density
ρs of the refrigerant at the suction side of the compressor 21 and
the density ρeo of the refrigerant at the outlets of the indoor heat
exchangers 31a to 31c (i.e., the inlet of the second gas refrigerant
communication pipes 72a to 72c). The density ρs of the refrigerant is
obtained by converting the suction pressure Ps and the suction
temperature Ts, and the density ρeo of the refrigerant is obtained by
converting the evaporation pressure Pe, which is a converted value of the
evaporation temperature Te, and the outlet temperature Teo of each of the
indoor heat exchangers 31a to 31c. In addition, the volume Vgpl2 of the
low pressure gas side refrigerant flow path in the connection units 4a to
4c (including up to the second bypass on/off valves V13a to V13c on the
low pressure gas side in the third bypass refrigerant circuits 43a to
43c) is a value that is known prior to installation of the connection
units 4a to 4c at the installation location and is stored in advance in
the memory of the controller 8.

[0178]A relational expression between a refrigerant quantity Mog2 in the
first low pressure gas pipe portion H and the operation state quantity of
constituent equipment or refrigerant flowing in the refrigerant circuit
10 is expressed, for example, by

Mog2=Vog2×ρoh,

which is a function expression in which a volume Vog2 of the first low
pressure gas pipe portion H in the outdoor unit 2 is multiplied by the
density ρoh of the refrigerant in the first low pressure gas pipe
portion H. Note that, the volume Vog2 of the first low pressure gas pipe
portion H is a value that is known prior to shipment to the installation
location and is stored in advance in the memory of the controller 8.

[0179]A relational expression between a refrigerant quantity Mog3 in the
second low pressure gas pipe portion I and the operation state quantity
of constituent equipment or refrigerant flowing in the refrigerant
circuit 10 is expressed, for example, by

Mog3=Vog3×ρs,

which is a function expression in which a volume Vog3 of the second low
pressure gas pipe portion I in the outdoor unit 2 is multiplied by the
density ρs of the refrigerant in the second low pressure gas pipe
portion I. Note that, the volume Vog3 of the second low pressure gas pipe
portion I is a value that is known prior to shipment to the installation
location and is stored in advance in the memory of the controller 8.

[0180]A relational expression between a refrigerant quantity Mob in the
second bypass circuit portion J and the operation state quantity of
constituent equipment or refrigerant flowing in the refrigerant circuit
10 is expressed, for example, by

Mob-kob1×ρco+kob2×ρs+kob3×Pc+kob4,

which is a function expression of the density ρco of the refrigerant
at the outlet of the outdoor heat exchanger 22, and the density ρs of
the refrigerant at the outlet on the bypass circuit side of the subcooler
24 and the evaporation pressure Pe. Note that, the parameters kob1 to
kob3 in the above described relational expression are derived from a
regression analysis of results of tests and detailed simulations and are
stored in advance in the memory of the controller 8. In addition, the
refrigerant quantity Mob of the second bypass circuit portion J may be
calculated using a simpler relational expression because the refrigerant
quantity in that portion is smaller compared to other portions. For
example, it is expressed as follows:

Mob=Vob×ρe×kob5,

which is a function expression in which a volume Vob of the second bypass
circuit portion J is multiplied by the saturated liquid density ρe at
the portion corresponding to the second bypass circuit side of the
subcooler 24 and a correct coefficient kob. Note that, the volume Vob of
the second bypass circuit portion J is a value that is known prior to
installation of the outdoor unit 2 at the installation location and is
stored in advance in the memory of the controller 8. In addition, the
saturated liquid density ρe at the portion on the second bypass
circuit side of the subcooler 24 is obtained by converting the suction
pressure Ps or the evaporation temperature Te.

[0181]Note that, in the present embodiment, one outdoor unit 2 is
provided. However, when a plurality of outdoor units are connected, as
for the refrigerant quantities in the outdoor unit such as Mog1, Mc,
Mol1, Mol2, Mog2, Mog3, and Mob, the relational expression for the
refrigerant quantity in each portion is set for each of the plurality of
outdoor units, and the entire refrigerant quantity in the outdoor units
is calculated by adding the refrigerant quantity in each portion of the
plurality of the outdoor units. Note that, relational expressions for the
refrigerant quantity in each portion having parameters with different
values will be used when a plurality of outdoor units with different
models and capacities are connected.

[0182]As described above, in the present embodiment, by using the
relational expressions for each portion in the refrigerant circuit 10,
the refrigerant quantity in each portion is calculated from the operation
state quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10 in the refrigerant quantity judging operation, and
thereby the refrigerant quantity in the refrigerant circuit 10 can be
calculated.

[0183]Further, this Step S12 is repeated until the condition for judging
the adequacy of the refrigerant quantity in the below described Step S13
is satisfied. Therefore, in the period from the start to the completion
of additional refrigerant charging, the refrigerant quantity in each
portion is calculated from the operation state quantity during
refrigerant charging by using the relational expressions for each portion
in the refrigerant circuit 10. More specifically, a refrigerant quantity
Mo in the outdoor unit 2, the refrigerant quantity Mr in each of the
indoor units 3a to 3c, and a refrigerant quantity Mbs in each of the
connection units 4a to 4c (=Vlp2×ρlp+Vgp2×ρgp) (i.e.,
the refrigerant quantity in each portion in the refrigerant circuit 10
excluding the first refrigerant communication pipe group 5 and the second
refrigerant communication pipe group 7) necessary for judgment of the
adequacy of the refrigerant quantity in the below described Step S13 are
calculated. Here, the refrigerant quantity Mo in the outdoor unit 2 is
calculated by adding the refrigerant quantity Mog1, Mc, Mol1, Mol2, Mog2,
Mog3, and Mob in the above described each portion in the outdoor unit 2.

[0184]In this way, the process in Step S12 is performed by the controller
8 that functions as the refrigerant quantity calculating means for
calculating the refrigerant quantity in each portion in the refrigerant
circuit 10 from the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 in the automatic
refrigerant charging operation.

[0185](Step S13: Judging the Adequacy of the Refrigerant Quantity)

[0186]As described above, when additional refrigerant charging into the
refrigerant circuit 10 starts, the refrigerant quantity in the
refrigerant circuit 10 gradually increases. Here, when the volume of the
first refrigerant communication pipe group 5 is unknown, the refrigerant
quantity that should be charged into the refrigerant circuit 10 after
additional refrigerant charging cannot be prescribed as the refrigerant
quantity in the entire refrigerant circuit 10. However, when the focus is
placed only on the outdoor unit 2, the indoor units 3a to 3c, and the
connection units 4a to 4c (i.e., the refrigerant circuit 10 excluding the
first refrigerant communication pipe group 5 and the second refrigerant
communication pipe group 7), it is possible to know in advance the
optimal refrigerant quantity in the outdoor unit 2 in the normal
operation mode by tests and detailed simulations. Therefore, additional
refrigerant can be charged by the following manner: a value of this
refrigerant quantity is stored as a target charging value Ms, in advance,
in the memory of the controller 8; the refrigerant quantity Mo in the
outdoor unit 2, the refrigerant quantity Mr in each of the indoor units
3a to 3c, and the refrigerant quantity Mbs in each of the connection
units 4a to 4c are calculated from the operation state quantity of
constituent equipment or refrigerant flowing in the refrigerant circuit
10 in the automatic refrigerant charging operation by using the above
described relational expressions; and additional refrigerant is charged
until a value of the sum of the above calculated refrigerant quantities
reaches the target charging value Ms. In other words, Step S13 is a
process to judge the adequacy of the refrigerant quantity charged into
the refrigerant circuit 10 by additional refrigerant charging by judging
whether or not the refrigerant quantity, which is obtained by adding the
refrigerant quantity Mo in the outdoor unit 2, the refrigerant quantity
Mr in the indoor units 3a to 3c, and the refrigerant quantity Mbs in the
connection units 4a to 4c in the automatic refrigerant charging
operation, has reached the target charging value Ms.

[0187]Then, in Step S13, when a value of the refrigerant quantity obtained
by adding the refrigerant quantity Mo in the outdoor unit 2, the
refrigerant quantity Mr in each of the indoor units 3a to 3c, and the
refrigerant quantity Mbs in each of the connection units 4a to 4c is
smaller than the target charging value Ms and additional refrigerant
charging has not been completed, the process in Step S13 is repeated
until the target charging value Ms is reached. In addition, when a value
of the refrigerant quantity obtained by adding the refrigerant quantity
Mo in the outdoor unit 2, the refrigerant quantity Mr in each of the
indoor units 3a to 3c, and the refrigerant quantity Mbs in each of the
connection units 4a to 4c reaches the target charging value Ms,
additional refrigerant charging is completed, and Step S1 as the
automatic refrigerant charging operation process is completed.

[0188]Note that, in the above described refrigerant quantity judging
operation, as the amount of additional refrigerant charged into the
refrigerant circuit 10 increases, a tendency of an increase in the
subcooling degree SCo at the outlet of the outdoor heat exchanger 22
appears, causing the refrigerant quantity Mc in the outdoor heat
exchanger 22 to increase, and the refrigerant quantity in other portions
tends to be maintained substantially constant. Therefore, the target
charging value Ms may be set as a value corresponding to only the
refrigerant quantity Mo in the outdoor unit 2 instead of corresponding to
all of the outdoor unit 2, the indoor units 3a to 3c, and the connection
units 4a to 4c; or may be set as a value corresponding to the refrigerant
quantity Mc in the outdoor heat exchanger 22, and additional refrigerant
may be charged until the target charging value Ms is reached under such
setting.

[0189]In this way, the process in Step S13 is performed by the controller
8 that functions as the refrigerant quantity judging means for judging
the adequacy of the refrigerant quantity in the refrigerant circuit 10 in
the refrigerant quantity judging operation of the automatic refrigerant
charging operation (i.e., for judging whether or not the refrigerant
quantity has reached the target charging value Ms).

[0190](Step S2: Pipe Volume Judging Operation)

[0191]When the above described automatic refrigerant charging operation in
Step S1 is completed, the process proceeds to the pipe volume judging
operation in Step S2. In the pipe volume judging operation, the process
from Step S21 to Step S25 as shown in FIG. 6 is performed by the
controller 8. Here, FIG. 6 is a flowchart of the pipe volume judging
operation.

[0193]In Step S21, as is the case with the above described refrigerant
quantity judging operation in Step S11 of the automatic refrigerant
charging operation as described above, the pipe volume judging operation
for the liquid refrigerant communication pipe portion B3, including the
all indoor unit operation, condensation pressure control, liquid pipe
temperature control, superheating degree control, and evaporation
pressure control, is performed. Here, the target liquid pipe temperature
Tlps of the temperature Tlp of the refrigerant at the outlet on the main
refrigerant circuit side of the subcooler 24 in the liquid pipe
temperature control is regarded as a first target value Tlps1, and the
state where the refrigerant quantity judging operation is stable at this
first target value Tlps1 is regarded as a first state (see the
refrigerating cycle indicated by lines including dotted lines in FIG. 7).
Note that, FIG. 7 is a Mollier diagram to show the refrigerating cycle of
the air conditioner 1 in the pipe volume judging operation for the liquid
refrigerant communication pipe.

[0194]Next, the first state where the temperature Tlp of the refrigerant
at the outlet on the main refrigerant circuit side of the subcooler 24 in
liquid pipe temperature control is stable at the first target value Tlps1
is switched to a second state (see the refrigerating cycle indicated by
solid lines in FIG. 7) where the target liquid pipe temperature Tlps is
changed to a second target value Tlps2 different from the first target
value Tlps1 and stabilized without changing the conditions for other
equipment controls, i.e., the conditions for the condensation pressure
control, superheating degree control, and evaporation pressure control
(i.e., without changing the target superheating degree SHrs and the
target low pressure Tes). In the present embodiment, the second target
value Tlps2 is a temperature higher than the first target value Tlps1.

[0195]In this way, by changing from the stable state at the first state to
the second state, the density of the refrigerant in the liquid
refrigerant communication pipe portion B3 decreases, and therefore the
refrigerant quantity Mlp in the liquid refrigerant communication pipe
portion B3 in the second state decreases compared to the refrigerant
quantity in the first state. Then, the refrigerant whose quantity has
decreased in the liquid refrigerant communication pipe portion B3 moves
to other portions in the refrigerant circuit 10. More specifically, as
described above, the conditions for other equipment controls other than
the liquid pipe temperature control are not changed, and therefore the
refrigerant quantity Mog1 in the high pressure gas pipe portion E, the
refrigerant quantity Mog2 in the first low pressure gas pipe portion H,
the refrigerant quantity Mog3 in the second low pressure gas pipe portion
I, and the refrigerant quantity Mgph in the high pressure gas refrigerant
communication pipe portion G1 and the refrigerant quantity Mgp1 in the
low pressure gas refrigerant communication pipe portion G2 are maintained
substantially constant, and the refrigerant whose quantity has decreased
in the liquid refrigerant communication pipe portion B3 will move to the
condenser portion A, the high temperature side liquid pipe portion B1,
the low temperature side liquid pipe portion B2, the indoor unit portion
F, and the second bypass circuit portion J. In other words, the
refrigerant quantity Mc in the condenser portion A, the refrigerant
quantity Mol1 in the high temperature side liquid pipe portion B1, the
refrigerant quantity Mol2 in the low temperature side liquid pipe portion
B2, the refrigerant quantity Mr in the indoor unit portion F, and the
refrigerant quantity Mob in the second bypass circuit portion J will
increase by the quantity of the refrigerant that has decreased in the
liquid refrigerant communication pipe portion B3.

[0196]Such control as described above is performed as the process in Step
S21 by the controller 8 (more specifically, by the indoor side
controllers 34a to 34c, the connection side controllers 44a to 44c, the
outdoor side controller 26, and the transmission line 8a that
interconnects each of the controllers 34a to 34c, 44a to 44c, and 26)
that functions as a pipe volume judging operation controlling means for
performing the pipe volume judging operation to calculate the refrigerant
quantity Mlp of the liquid refrigerant communication pipe portion B3.

[0197]Next, in Step S22, the volume Vlp of the liquid refrigerant
communication pipe portion B3 is calculated by utilizing a phenomenon
that the refrigerant quantity in the liquid refrigerant communication
pipe portion B3 decreases and the refrigerant whose quantity has
decreased moves to other portions in the refrigerant circuit 10 because
of the change from the first state to the second state.

[0198]First, a calculation formula used in order to calculate the volume
Vlp of the liquid refrigerant communication pipe portion B3 is described.
Provided that the quantity of the refrigerant that has decreased in the
liquid refrigerant communication pipe portion B3 and moved to other
portions in the refrigerant circuit 10 by the above described pipe volume
judging operation is a refrigerant increase/decrease quantity ΔMlp,
and that the increase/decrease quantities of the refrigerant in each
portion between the first state and the second state are ΔMc,
ΔMol1, ΔMol2, ΔMr, and ΔMob (here, the
refrigerant quantity Mog1, the refrigerant quantity Mog2, the refrigerant
quantity Mog3, the refrigerant quantity Mgph, and the refrigerant
quantity Mgp1 are omitted because they are maintained substantially
constant), the refrigerant increase/decrease quantity ΔMlp can be,
for example, calculated by the following function expression:

ΔMlp=-(ΔMc+ΔMol1+ΔMol2+ΔMr+ΔMob).

Then, the value of ΔMlp is divided by a density change quantity
Δρlp of the refrigerant between the first state and the second
state in the liquid refrigerant communication pipe portion B3, and
thereby the volume Vlp of the liquid refrigerant communication pipe
portion B3 can be calculated. Note that, although there is little effect
on a calculation result of the refrigerant increase/decrease quantity
ΔMlp, the refrigerant quantity Mog1 and the refrigerant quantity
Mog2 may be included in the above described function expression.

Vlp=ΔMlp/Δρlp

[0199]In addition, the volume Vlp2 of the liquid side refrigerant flow
path in the connection units 4a to 4c is a value that is known prior to
installation of the connection units 4a to 4c at the installation
location. Thus, it is possible to determine the volume Vlp1 of the
portion combining the first liquid refrigerant communication pipe 51 and
the second liquid refrigerant communication pipes 71a to 71c, which are
the refrigerant pipes arranged on site when installing the air
conditioner 1 at an installation location such as a building and the
like, by subtracting the volume Vlp2 from the volume Vlp of the liquid
refrigerant communication pipe portion B3, which is determined by the
calculation.

[0200]Note that, ΔMc, ΔMol1, ΔMol2, ΔMr, and
ΔMob can be obtained by calculating the refrigerant quantity in the
first state and the refrigerant quantity in the second state by using the
above described relational expression for each portion in the refrigerant
circuit 10 and further by subtracting the refrigerant quantity in the
first state from the refrigerant quantity in the second state. In
addition, the density change quantity Δρlp can be obtained by
calculating the density of the refrigerant at the outlet of the subcooler
24 in the first state and the density of the refrigerant at the outlet of
the subcooler 24 in the second state and further by subtracting the
density of the refrigerant in the first state from the density of the
refrigerant in the second state.

[0201]By using the calculation formula as described above, the volume Vlp
of the liquid refrigerant communication pipe portion B3 can be calculated
from the operation state quantity of constituent equipment or refrigerant
flowing in the refrigerant circuit 10 in the first and second states.

[0202]Note that, in the present embodiment, the state is changed such that
the second target value Tlps2 in the second state becomes a temperature
higher than the first target value Tlps1 in the first state and therefore
the refrigerant in the low temperature side liquid pipe portion B2 is
moved to other portions to increase the refrigerant quantity in other
portions; thereby the volume Vlp of the liquid refrigerant communication
pipe portion B3 is calculated from the increased quantity. However, the
state may be changed such that the second target value Tlps2 in the
second state becomes a temperature lower than the first target value
Tlps1 in the first state and therefore the refrigerant is moved from
other portions to the liquid refrigerant communication pipe portion B3 to
decrease the refrigerant quantity in other portions; thereby the volume
Vlp of the liquid refrigerant communication pipe portion B3 is calculated
from the decreased quantity.

[0203]In this way, the process in Step S22 is performed by the controller
8 that functions as the pipe volume calculating means for the liquid
refrigerant communication pipe, which calculates the volume Vlp of the
liquid refrigerant communication pipe portion B3 from the operation state
quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10 in the pipe volume judging operation for the
liquid refrigerant communication pipe portion B3.

[0205]After the above described Step S21 and Step S22 are completed, the
pipe volume judging operation for the gas refrigerant communication pipe
portion G, including the all indoor unit operation, condensation pressure
control, liquid pipe temperature control, superheating degree control,
and evaporation pressure control, is performed in Step S23. Here, the
target low pressure Pes of the suction pressure Ps of the compressor 21
in the evaporation pressure control is regarded as a first target value
Pes1, and the state where the refrigerant quantity judging operation is
stable at this first target value Pes1 is regarded as a first state (see
the refrigerating cycle indicated by lines including dotted lines in FIG.
8). Note that FIG. 8 is a Mollier diagram to show the refrigerating cycle
of the air conditioner 1 in the pipe volume judging operation for the gas
refrigerant communication pipe.

[0206]Next, the first state where the target low pressure Pes of the
suction pressure Ps in the compressor 21 in evaporation pressure control
is stable at the first target value Pes1 is switched to a second state
(see the refrigerating cycle indicated only by solid lines in FIG. 8)
where the target low pressure Pes is changed to a second target value
Pes2 different from the first target value Pes1 and stabilized without
changing the conditions for other equipment controls, i.e., without
changing the conditions for the liquid pipe temperature control, the
condensation pressure control, and the superheating degree control (i.e.,
without changing the target liquid pipe temperature Tlps and the target
superheating degree SHrs). In the present embodiment, the second target
value Pes2 is a pressure lower than the first target value Pes1.

[0207]In this way, by changing from the stable state at the first state to
the second state, the density of the refrigerant in the gas refrigerant
communication pipe portion G decreases, and therefore the refrigerant
quantity Mgp in the gas refrigerant communication pipe portion G in the
second state decreases compared to the refrigerant quantity in the first
state. Then, the refrigerant whose quantity has decreased in the gas
refrigerant communication pipe portion G will move to other portions in
the refrigerant circuit 10. More specifically, as described above, the
conditions for other equipment controls other than the evaporation
pressure control are not changed, and therefore the refrigerant quantity
Mog1 in the high pressure gas pipe portion E, the refrigerant quantity
Mol1 in the high temperature side liquid pipe portion B1, the refrigerant
quantity Mol2 in the low temperature side liquid pipe portion B2, and the
refrigerant quantity Mlp in the liquid refrigerant communication pipe
portion B3 are maintained substantially constant, and the refrigerant
whose quantity has decreased in the gas refrigerant communication pipe
portion G will move to the first low pressure gas pipe portion H, the
second low pressure gas pipe portion I, the condenser portion A, the
indoor unit portion F, and the second bypass circuit portion J. In other
words, the refrigerant quantity Mog2 in the first low pressure gas pipe
portion H, the refrigerant quantity Mog3 in the second low pressure gas
pipe portion I, the refrigerant quantity Mc in the condenser portion A,
the refrigerant quantity Mr in the indoor unit portion F, and the
refrigerant quantity Mob in the second bypass circuit portion J will
increase by the quantity of the refrigerant that has decreased in the gas
refrigerant communication pipe portion G.

[0208]Such control as described above is performed as the process in Step
S23 by the controller 8 (more specifically, by the indoor side
controllers 34a to 34c, the connection side controllers 44a to 44c, the
outdoor side controller 26, and the transmission line 8a that
interconnects each of the controllers 34a to 34c, 44a to 44c, and 26)
that functions as the pipe volume judging operation controlling means for
performing the pipe volume judging operation to calculate the volume Vgp
of the gas refrigerant communication pipe portion G.

[0209]Next in Step S24, the volume Vgp of the gas refrigerant
communication pipe portion G is calculated by utilizing a phenomenon that
the refrigerant quantity in the gas refrigerant communication pipe
portion G decreases and the refrigerant whose quantity has decreased
moves to other portions in the refrigerant circuit 10 because of the
change from the first state to the second state.

[0210]First, a calculation formula used in order to calculate the volume
Vgp of the gas refrigerant communication pipe portion G is described.
Provided that the quantity of the refrigerant that has decreased in the
gas refrigerant communication pipe portion G and moved to other portions
in the refrigerant circuit 10 by the above described pipe volume judging
operation is a refrigerant increase/decrease quantity ΔMgp, and
that the increase/decrease quantities of the refrigerant in each portion
between the first state and the second state are ΔMc, ΔMog2,
ΔMog3, ΔMr, and ΔMob (here, the refrigerant quantity
Mog1, the refrigerant quantity Mol1, the refrigerant quantity Mol2, and
the refrigerant quantity Mlp are omitted because they are maintained
substantially constant), the refrigerant increase/decrease quantity
ΔMgp can be, for example, calculated by the following function
expression:

ΔMgp=-(ΔMc+ΔMog2+ΔMog3+ΔMr+ΔMob).

Then, the value of ΔMgp is divided by a density change quantity
Δρgp of the refrigerant between the first state and the second
state in the gas refrigerant communication pipe portion G, and thereby
the volume Vgp of the gas refrigerant communication pipe portion G can be
calculated. Note that, although there is little effect on a calculation
result of the refrigerant increase/decrease quantity ΔMgp, the
refrigerant quantity Mog1, the refrigerant quantity Mol1, and the
refrigerant quantity Mol2 may be included in the above described function
expression.

Vgp=ΔMgp/Δρgp

Note that, ΔMc, ΔMog 2, ΔMog 3, ΔMr and ΔMob
can be obtained by calculating the refrigerant quantity in the first
state and the refrigerant quantity in the second state by using the above
described relational expression for each portion in the refrigerant
circuit 10 and further by subtracting the refrigerant quantity in the
first state from the refrigerant quantity in the second state. In
addition, the density change quantity Δρgp can be obtained by
calculating an average density among the density ρs of the
refrigerant at the suction side of the compressor 21, the density ρoh
of the refrigerant in the pipe on the high pressure gas side between the
high pressure gas side stop valve V5 and the first high pressure gas
on/off valve V8 in the outdoor unit 2, the density ρbsh of the
refrigerant in the high pressure gas side refrigerant flow path in the
connection units 4a to 4c, and the density ρeo of the refrigerant at
the outlets of the indoor heat exchangers 31a to 31c in the first state
and by subtracting the average density in the first state from the
average density in the second state.

[0211]By using such calculation formula as described above, the volume Vgp
of the gas refrigerant communication pipe portion G can be calculated
from the operation state quantity of constituent equipment or the
refrigerant flowing in the refrigerant circuit 10 in the first and second
states.

[0212]In addition, the volume Vgp2 of the high pressure gas side
refrigerant flow path and the low pressure gas side refrigerant flow path
(including a portion corresponding to the third bypass refrigerant
circuits 43a to 43c) in the connection units 4a to 4c is a value that is
known prior to installation of the connection units 4a to 4c at the
installation location. Thus, it is possible to determine the volume Vgp1
of the portion combining the high pressure gas refrigerant communication
pipe 52, the low pressure gas refrigerant communication pipe 53, and the
second gas refrigerant communication pipes 72a to 72c, which are the
refrigerant pipes arranged on site when installing the air conditioner 1
at an installation location such as a building and the like, by
subtracting the volume Vgp2 from the volume Vgp of the gas refrigerant
communication pipe portion Q which is determined by the calculation.

[0213]Note that, in the present embodiment, the state is changed such that
the second target value Pes2 in the second state becomes a pressure lower
than the first target value Pes1 in the first state and therefore the
refrigerant in the gas refrigerant communication pipe portion G is moved
to other portions to increase the refrigerant quantity in other portions;
thereby the volume Vlp in the gas refrigerant communication pipe portion
G is calculated from the increased quantity. However, the state may be
changed such that the second target value Pes2 in the second state
becomes a pressure higher than the first target value Pes1 in the first
state and therefore the refrigerant is moved from other portions to the
gas refrigerant communication pipe portion G to decrease the refrigerant
quantity in other portions; thereby the volume Vlp of the gas refrigerant
communication pipe portion G may be calculated from the decreased
quantity.

[0214]In this way, the process in Step S24 is performed by the controller
8 that functions as the pipe volume calculating means for a gas
refrigerant communication pipe, which calculates the volume Vgp of the
gas refrigerant communication pipe portion G from the operation state
quantity of constituent equipment or the refrigerant flowing in the
refrigerant circuit 10 during the pipe volume judging operation for the
gas refrigerant communication pipe portion G.

[0215](Step S25: Judging the Validity of a Result of Pipe Volume Judging
Operation)

[0216]After the above described Step S21 to Step S24 are completed, in
Step S25, whether or not a result of the pipe volume judging operation is
valid, in other words, whether or not the volume Vlp of the liquid
refrigerant communication pipe portion B3 and the volume Vgp of the gas
refrigerant communication pipe portion G calculated by the pipe volume
calculating means are valid is judged.

[0217]Specifically, as shown in an inequality expression below, it is
judged by whether or not the ratio of the volume Vlp of the liquid
refrigerant communication pipe portion B3 to the volume Vgp of the gas
refrigerant communication pipe portion G obtained by the calculations is
in a predetermined numerical value range.

ε1<Vlp/Vgp<ε2

Here, ε1 and ε2 are values that are changed based on the
minimum value and the maximum value of the pipe volume ratio in feasible
combinations of the heat source unit and the utilization unit.

[0218]Then, when the volume ratio Vlp/Vgp satisfies the above described
numerical value range, the process in Step S2 for the pipe volume judging
operation is completed. When the volume ratio Vlp/Vgp does not satisfy
the above numerical value range, the process for the pipe volume judging
operation and the volume calculation in Step S21 to Step S24 is performed
again.

[0219]In this way, the process in Step S25 is performed by the controller
8 that functions as a validity judging means for judging whether or not a
result of the above described pipe volume judging operation is valid, in
other words, whether or not the volume Vlp of the liquid refrigerant
communication pipe portion B3 and the volume Vgp of the gas refrigerant
communication pipe portion G calculated by the pipe volume calculating
means are valid.

[0220]Note that, in the present embodiment, the pipe volume judging
operation (Steps S21, S22) for the liquid refrigerant communication pipe
portion B3 is first performed and then the pipe volume judging operation
for the gas refrigerant communication pipe portion G (Steps S23, S24) is
performed. However, the pipe volume judging operation for the gas
refrigerant communication pipe portion G may be performed first.

[0221]In addition, in the above described Step S25, when a result of the
pipe volume judging operation in Steps S21 to S24 is judged to be invalid
a plurality of times, or when it is desired to more simply judge the
volume Vlp of the liquid refrigerant communication pipe portion B3 and
the volume Vgp of the gas refrigerant communication pipe portion Q
although it is not shown in FIG. 6, for example, in Step S25, after a
result of the pipe volume judging operation in Steps S21 to S24 is judged
to be invalid, it is possible to proceed to the process for estimating,
from the pressure loss in a portion combining the liquid refrigerant
communication pipe portion B3 and the gas refrigerant communication pipe
portion G (hereinafter referred to as "refrigerant communication pipe
portion K"), the length of the refrigerant communication pipe portion K
and calculating the volume Vlp of the liquid refrigerant communication
pipe portion B3 and the volume Vgp of the gas refrigerant communication
pipe portion G from the estimated pipe length and an average volume
ratio, thereby obtaining the volume Vlp of the liquid refrigerant
communication pipe portion B3 and the volume Vgp of the gas refrigerant
communication pipe portion G.

[0222]In addition, in the present embodiment, the case where the pipe
volume judging operation is performed to calculate the volume Vlp of the
liquid refrigerant communication pipe portion B3 and the volume Vgp of
the gas refrigerant communication pipe portion G is described on the
premise that there is no information regarding the length, pipe diameter
and the like of the refrigerant communication pipe portion K, and the
volume Vlp of the liquid refrigerant communication pipe portion B3 and
the volume Vgp of the gas refrigerant communication pipe portion G are
unknown. However, when the pipe volume calculating means has a function
to calculate the volume Vlp of the liquid refrigerant communication pipe
portion B3 and the volume Vgp of the gas refrigerant communication pipe
portion G by inputting information regarding the length, pipe diameters
and the like of the refrigerant communication pipe portion K, such
function may be used together.

[0223]Further, when the above described function to calculate the volume
Vlp of the liquid refrigerant communication pipe portion B3 and the
volume Vgp of the gas refrigerant communication pipe portion G by the
pipe volume judging operation and by using the operation results is not
used but only the function to calculate the volume Vlp of the liquid
refrigerant communication pipe portion B3 and the volume Vgp of the gas
refrigerant communication pipe portion G by inputting information
regarding the length, pipe diameter and the like of the refrigerant
communication pipe portion K is used, the above described validity
judging means (Step S25) may be used to judge whether or not the input
information regarding the lengths, pipe diameters and the like of the
refrigerant communication pipe portion K is valid.

[0224](Step S3: Initial Refrigerant Quantity Detection Operation)

[0225]When the above described pipe volume judging operation of Step S2 is
completed, the process proceeds to the initial refrigerant quantity
detection operation of Step S3. In the initial refrigerant quantity
detection operation, the process in Step S31 and Step S32 shown in FIG. 9
is performed by the controller 8. Here, FIG. 9 is a flowchart of the
initial refrigerant quantity detection operation.

[0226](Step S31: Refrigerant Quantity Judging Operation)

[0227]In Step S31, as is the case with the above described refrigerant
quantity judging operation of Step S11 in the automatic refrigerant
charging operation, the refrigerant quantity judging operation, including
the all indoor unit operation, condensation pressure control, liquid pipe
temperature control, superheat degree control, and evaporation pressure
control, is performed. Here, as a rule, values to be used for the target
liquid pipe temperature value Tlps in the liquid pipe temperature
control, the target superheat degree value SHrs in the superheat degree
control, and the target low pressure value Pes in the evaporation
pressure control are same as the target values during the refrigerant
quantity judging operation of Step S1 in the automatic refrigerant
charging operation.

[0228]In this way, the process in Step S31 is performed by the controller
8 that functions as the refrigerant quantity judging operation
controlling means for performing the refrigerant quantity judging
operation including the all indoor unit operation, condensation pressure
control, liquid pipe temperature control, superheat degree control, and
evaporation pressure control.

[0229](Step S32: Refrigerant Quantity Calculation)

[0230]Next, the refrigerant quantity in the refrigerant circuit 10 is
calculated from the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 in the initial
refrigerant quantity detection operation in Step S32 by the controller 8
that functions as the refrigerant quantity calculating means while
performing the above described refrigerant quantity judging operation.
Calculation of the refrigerant quantity in the refrigerant circuit 10 is
performed by using the above described relational expression between the
refrigerant quantity in each portion in the refrigerant circuit 10 and
the operation state quantity of constituent equipment or refrigerant
flowing in the refrigerant circuit 10. However, at this time, the volume
Vlp of the liquid refrigerant communication pipe portion B3 and the
volume Vgp of the gas refrigerant communication pipe portion Q which were
unknown at the time of after installation of constituent equipment of the
air conditioner 1, have been calculated and the values thereof are known
by the above described pipe volume judging operation. Thus, by
multiplying the volume Vlp of the liquid refrigerant communication pipe
portion B3 and the volume Vgp of the gas refrigerant communication pipe
portion G by the density of the refrigerant, the refrigerant quantity Mlp
in the liquid refrigerant communication pipe portion B3 and the
refrigerant quantity Mgp in the gas refrigerant communication pipe
portion G can be calculated, and further by adding the refrigerant
quantity in each of other portions, the initial refrigerant quantity in
the entire refrigerant circuit 10 can be detected. This initial
refrigerant quantity is used as a reference refrigerant quantity Mi of
the entire refrigerant circuit 10, which serves as a reference for
judging whether or not there is a refrigerant leak from the refrigerant
circuit 10 during the below described refrigerant leak detection
operation. Therefore, it is stored as a value of the operation state
quantity in the memory of the controller 8 serving as the state quantity
storing means.

[0231]In this way, the process in Step S32 is performed by the controller
8 that functions as the refrigerant quantity calculating means for
calculating the refrigerant quantity in each portion in the refrigerant
circuit 10 from the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 in the initial
refrigerant quantity detection operation.

[0232]<Refrigerant Leak Detection Operation Mode>

[0233]Next, the refrigerant leak detection operation mode is described
with reference to FIGS. 1, 2, 5, and 10. Here, FIG. 10 is a flowchart of
the refrigerant leak detection operation mode.

[0234]In the present embodiment, an example of a case is described where,
whether or not the refrigerant in the refrigerant circuit 10 is leaking
to the outside due to an unforeseen factor is detected periodically (for
example, during a period of time such as on a holiday or in the middle of
the night when air conditioning is not needed).

[0235](Step S41: Refrigerant Quantity Judging Operation)

[0236]First, when operation in the normal operation mode such as the above
described cooling operation and heating operation has gone on for a
certain period of time (for example, half a year to a year), the normal
operation mode is automatically or manually switched to the refrigerant
leak detection operation mode, and as is the case with the refrigerant
quantity judging operation of the initial refrigerant quantity detection
operation, the refrigerant quantity judging operation, including the all
indoor unit operation, condensation pressure control, liquid pipe
temperature control, superheating degree control, and evaporation
pressure control, is performed. Here, as a rule, values that are the same
as the target values in Step S31 of the refrigerant quantity judging
operation of the initial refrigerant quantity detection operation are
used for the target liquid pipe temperature Tlps in the liquid pipe
temperature control, the target superheating degree SHrs in the
superheating degree control, and the target low pressure Pes in the
evaporation pressure control.

[0237]Note that, this refrigerant quantity judging operation is performed
for each time the refrigerant leak detection operation is performed. Even
when the refrigerant temperature Tco at the outlet of the outdoor heat
exchanger 22 changes due to the different operating conditions, for
example, such as when the condensation pressure Pc is different or when
the refrigerant is leaking, the refrigerant temperature Tlp in the liquid
refrigerant communication pipe portion B3 is maintained constant at the
same target liquid pipe temperature Tlps by the liquid pipe temperature
control.

[0238]In this way, the process in Step S41 is performed by the controller
8 that functions as the refrigerant quantity judging operation
controlling means for performing the refrigerant quantity judging
operation, including the all indoor unit operation, condensation pressure
control, liquid pipe temperature control, superheating degree control,
and evaporation pressure control.

[0239](Step S42: Refrigerant Quantity Calculation)

[0240]Next, the refrigerant quantity in the refrigerant circuit 10 is
calculated from the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 in the refrigerant leak
detection operation in Step S42 by the controller 8 that functions as the
refrigerant quantity calculating means while performing the above
described refrigerant quantity judging operation. Calculation of the
refrigerant quantity in the refrigerant circuit 10 is performed by using
the above described relational expression between the refrigerant
quantity in each portion in the refrigerant circuit 10 and the operation
state quantity of constituent equipment or refrigerant flowing in the
refrigerant circuit 10. However, at this time, as is the case with the
initial refrigerant quantity detection operation, the volume Vlp of the
liquid refrigerant communication pipe portion B3 and the volume Vgp of
the gas refrigerant communication pipe portion G, which were unknown at
the time of after installation of constituent equipment of the air
conditioner 1, have been calculated and the values thereof are known by
the above described pipe volume judging operation. Thus, by multiplying
the volume Vlp of the liquid refrigerant communication pipe portion B3
and the volume Vgp of the gas refrigerant communication pipe portion G by
the density of the refrigerant, the refrigerant quantity Mlp in the
liquid refrigerant communication pipe portion B3 and the refrigerant
quantity Mgp in the gas refrigerant communication pipe portion G can be
calculated, and further by adding the refrigerant quantity in each of
other portions, the refrigerant quantity M in the entire refrigerant
circuit 10 can be calculated.

[0241]Here, as described above, the refrigerant temperature Tlp in the
liquid refrigerant communication pipe portion B3 is maintained constant
at the target liquid pipe temperature Tlps by the liquid pipe temperature
control. Therefore, regardless of the difference in the operating
conditions for the refrigerant leak detection operation, the refrigerant
quantity Mlp in the liquid refrigerant communication pipe portion B3 will
be maintained constant even when the refrigerant temperature Tco at the
outlet of the outdoor heat exchanger 22 changes.

[0242]In this way, the process in Step S42 is performed by the controller
8 that functions as the refrigerant quantity calculating means for
calculating the refrigerant quantity at each portion in the refrigerant
circuit 10 from the operation state quantity of constituent equipment or
refrigerant flowing in the refrigerant circuit 10 in the refrigerant leak
detection operation.

[0244]When refrigerant leaks from the refrigerant circuit 10, the
refrigerant quantity in the refrigerant circuit 10 decreases. Then, when
the refrigerant quantity in the refrigerant circuit 10 decreases, mainly,
a tendency of a decrease in the subcooling degree SCo at the outlet of
the outdoor heat exchanger 22 appears. Along with this, the refrigerant
quantity Mc in the outdoor heat exchanger 22 decreases, and the
refrigerant quantities in other portions tend to be maintained
substantially constant. Consequently, the refrigerant quantity M of the
entire refrigerant circuit 10 calculated in the above described Step S42
is smaller than the reference refrigerant quantity Mi detected in the
initial refrigerant quantity detection operation when the refrigerant is
leaking from the refrigerant circuit 10; whereas when the refrigerant is
not leaking from the refrigerant circuit 10, the refrigerant quantity M
is substantially the same as the reference refrigerant quantity Mi.

[0245]By utilizing the above-described characteristics, whether or not the
refrigerant is leaking is judged in Step S43. When it is judged in Step
S43 that the refrigerant is not leaking from the refrigerant circuit 10,
the refrigerant leak detection operation mode is finished.

[0246]On the other hand, when it is judged in Step S43 that the
refrigerant is leaking from the refrigerant circuit 10, the process
proceeds to Step S44, and a warning indicating that a refrigerant leak is
detected is displayed on the warning display 9. Subsequently, the
refrigerant leak detection operation mode is finished.

[0247]In this way, the process from Steps S42 to S44 is performed by the
controller 8 that functions as a refrigerant leak detecting means, which
is one of the refrigerant quantity judging means, and which detects
whether or not the refrigerant is leaking by judging the adequacy of the
refrigerant quantity in the refrigerant circuit 10 while performing the
refrigerant quantity judging operation in the refrigerant leak detection
operation mode.

[0248]As described above, in the air conditioner 1 in the present
embodiment, the controller 8 functions as the refrigerant quantity
judging operation means, the refrigerant quantity calculating means, the
refrigerant quantity judging means, the pipe volume judging operation
means, the pipe volume calculating means, the validity judging means, and
the state quantity storing means, and thereby configures the refrigerant
quantity judging system for judging the adequacy of the refrigerant
quantity charged into the refrigerant circuit 10.

(3) CHARACTERISTICS OF THE AIR CONDITIONER

[0249](A)

[0250]With this air conditioner 1, when performing the refrigerant
quantity judging operation while the indoor units 3a to 3c in all the
rooms are set to the cooling operation state, the high pressure gas
refrigerant communication pipe portion G1 extending from the outdoor unit
2 to the connection units 4a to 4c will be in a shut-off state. Thereby
the refrigerant condenses and accumulates in the pipe, and thus the
detection error may be increased. Therefore, the first bypass refrigerant
circuit 27 and the third bypass refrigerant circuits 43a to 43c which
bypass the high pressure gas refrigerant communication pipe portion G1 to
the low pressure gas refrigerant communication pipe portion G2 are
provided, and the first bypass on/off valve V3 and the second bypass
on/off valves V13a to V13c are set to an opened state during the
refrigerant quantity judging operation, thereby reducing the pressure
difference between the high pressure gas refrigerant communication pipe
portion G1 and the low pressure gas refrigerant communication pipe
portion G2 and preventing accumulation of liquid refrigerant in the high
pressure gas refrigerant communication pipe portion G1 resulting from
condensation. Thus, the refrigerant quantity judging operation with high
accuracy can be achieved. In addition, the first bypass on/off valve V3
and the third bypass on/off valves are provided in the outdoor unit 2 and
in the connection units 4a to 4c, respectively. The first bypass on/off
valve V3 is provided in the outdoor unit 2, and the third bypass on/off
valves are provided in the connection units 4a to 4c. By using these
valves in combination, the low pressure gas refrigerant can easily flow
through the high pressure gas refrigerant communication pipe portion G1,
and the temperature change of the gas refrigerant can be minimized. Thus,
the detection error can be reduced. In addition, the bypass circuit can
be provided in the refrigerant circuit 10 even without laying pipes for
the bypass circuit at the time of construction. Accordingly, it is
possible to reduce the labors for construction and the cost.

[0251](B)

[0252]This air conditioner 1 is further provided with the temperature
sensor in the high pressure gas refrigerant communication pipe portion
G1. Accordingly, even when the temperate of the gas refrigerant in the
high pressure gas refrigerant communication pipe portion G1 changes
because of the incoming heat from the outside air and the like and
thereby the density of the refrigerant changes, it is possible to correct
the density of the refrigerant based on the temperature detection value
by the temperature sensor. Thereby it is possible to reduce the detection
error. Thus, the refrigerant quantity judging operation with higher
accuracy can be achieved. In addition, with this air conditioner 1, in
the high pressure gas refrigerant communication pipe portion G1, the
first high pressure gas pipe temperature sensor T8 is provided in the
heat source unit, and the second high pressure gas pipe temperature
sensors T12a to T12c are provided in the connection units 4a to 4c.
Accordingly, by using the first high pressure gas pipe temperature sensor
T8 and the second high pressure gas pipe temperature sensors T12a to T12c
in combination, it is possible to more accurately correct the density of
the refrigerant in the pipe. In addition, the temperature detecting means
can be provided in the refrigerant circuit 10 even without providing the
temperature sensor in the high pressure gas refrigerant pipe at the time
of construction. Therefore, it is possible to reduce the labors for
construction and the cost.

(4) ALTERNATIVE EMBODIMENT

[0253]While a preferred embodiment of the present invention has been
described with reference to the figures, the scope of the present
invention is not limited to the above embodiment, and the various changes
and modifications may be made without departing from the scope of the
present invention.

[0254](A)

[0255]In the above described embodiment, an example in which the present
invention is applied to an air conditioner including a single outdoor
unit is described. However, it is not limited thereto, and the present
invention may be applied to an air conditioner including a plurality of
outdoor units. In addition, although an air-cooled outdoor unit that uses
the outdoor air as the heat source is used as the outdoor unit 2 of the
air conditioner 1, a water-cooled type or ice thermal storage type
outdoor unit may be used instead.

[0256](B)

[0257]In the above described embodiment, as the bypass circuits, the first
bypass refrigerant circuit 27 is provided on the outdoor unit 2 side and
the third bypass refrigerant circuits 43a to 43c are provided on the
connection units 4a to 4c side. However, the bypass circuits may be
provided only on the outdoor unit 2 side or only on the connection units
4a to 4c side.

[0258](C)

[0259]In the above described embodiment, as the temperature sensors, the
first high pressure gas pipe temperature sensor T8 is mounted on the
outdoor unit 2 side and the second high pressure gas pipe temperature
sensors T12a to T12c are mounted on the connection units 4a to 4c side.
However, the temperature sensors may be mounted only on the outdoor unit
2 side or only on the connection units 4a to 4c side. In addition, the
temperature sensors may not necessarily be provided.

[0260](D)

[0261]The controller 8 that performs the operation control of the entire
air conditioner 1 is configured by the outdoor side controller 26, the
indoor side controllers 34a to 34c, and the connection side controllers
44a to 44c as they exchange control signals via the transmission line 8a.
However, it is not limited thereto. A controller that performs the
operation control of the entire air conditioner 1 may be provided in the
outdoor unit 2, in the indoor units 3a to 3c, or in the connection units
4a to 4c; or, a single unit may be provided as a control unit.

INDUSTRIAL APPLICABILITY

[0262]The air conditioner according to the present invention reduces the
pressure difference between the first gas refrigerant communication pipe
and the second gas refrigerant communication pipe, prevents accumulation
of liquid refrigerant in the first gas refrigerant communication pipe
resulting from condensation, and can perform the refrigerant quantity
judging operation with high accuracy. Thus, the present invention is
useful as a refrigerant circuit of an air conditioner, an air conditioner
provided therewith, and the like.